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Detection of alpha particles using DNAAl Schottky junctionsHassan Maktuff Jaber Al-Taii Vengadesh Periasamy and Yusoff Mohd Amin Citation Journal of Applied Physics 118 114502 (2015) doi 10106314930888 View online httpdxdoiorg10106314930888 View Table of Contents httpscitationaiporgcontentaipjournaljap11811ver=pdfcov Published by the AIP Publishing Articles you may be interested in Vertically grown Ge nanowire Schottky diodes on Si and Ge substrates J Appl Phys 118 024301 (2015) 10106314923407 Electrical transport properties of isolated carbon nanotubeSi heterojunction Schottky diodes Appl Phys Lett 103 193111 (2013) 10106314829155 Forward current transport mechanisms in NiAu-AlGaNGaN Schottky diodes J Appl Phys 114 144511 (2013) 10106314824296 Extraction of voltage-dependent series resistance from I-V characteristics of Schottky diodes Appl Phys Lett 99 093505 (2011) 10106313633116 Analysis of temperature-dependent barrier heights in erbium-silicided Schottky diodes J Vac Sci Technol B 26 137 (2008) 10111612825172

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10318017 On Wed 30 Sep 2015 023845

Detection of alpha particles using DNAAl Schottky junctions

Hassan Maktuff Jaber Al-Tarsquoii12a) Vengadesh Periasamy1a) and Yusoff Mohd Amin3

1Low Dimensional Materials Research Centre (LDMRC) 50603 Kuala Lumpur Malaysia2Department of Physics Faculty of Science University of Al-Muthana Al-Muthana 66001 Iraq3Department of Physics Faculty of Science University of Malaya 50603 Kuala Lumpur Malaysia

(Received 9 June 2015 accepted 30 August 2015 published online 16 September 2015)

Deoxyribonucleic acid or DNA can be utilized in an organic-metallic rectifying structure to detect

radiation especially alpha particles This has become much more important in recent years due to

crucial environmental detection needs in both peace and war In this work we fabricated an alumi-

num (Al)DNAAl structure and generated currentndashvoltage characteristics upon exposure to alpha

radiation Two models were utilized to investigate these current profiles the standard conventional

thermionic emission model and Cheung and Cheungrsquos method Using these models the barrier

height Richardson constant ideality factor and series resistance of the metal-DNA-metal structure

were analyzed in real time The barrier height U value calculated using the conventional method

for non-radiated structure was 07149 eV increasing to 07367 eV after 4 min of radiation Barrier

height values were observed to increase after 20 30 and 40 min of radiation except for 6 8 and

10 min which registered a decrease of about 067 eV This was in comparison using Cheung and

Cheungrsquos method which registered 06983 eV and 07528 eV for the non-radiated and 2 min of

radiation respectively The barrier height values meanwhile were observed to decrease after 4

(061 eV) to 40 min (06945 eV) The study shows that conventional thermionic emission model

could be practically utilized for estimating the diode parameters including the effect of series resist-

ance These changes in the electronic properties of the AlDNAAl junctions could therefore be uti-

lized in the manufacture of sensitive alpha particle sensors VC 2015 AIP Publishing LLC

[httpdxdoiorg10106314930888]

INTRODUCTION

Radiation sensors are not only required in diagnostics

and imaging technologies but are also increasingly utilized

in medicine space technology industry and research12

These applications generally encompass various aspects such

as security imaging quality control treatment and safety

Sensors are devices that produce significant variation to a

well-known input stimulus This motivation can be a physi-

cal impetus similar to temperature or pressure or a concentra-

tion of a specific chemical or biochemical material3

The radiation effect on the active material utilized within

the sensing device therefore determines the function of the

sensor being developed4

There are six classes of sensors typically differentiated

by the energy transduced in the sensor These are thermal

optical electronic mechanical magnetic and electrochemi-

cal sensors3 DNA molecules are described as a double

stranded negatively charged polymer These negatively

charged molecules can modify the interfacial electronic

states of metalsilicon semiconductor structures DNA in

recent years has been a material of choice due to its proper-

ties in terms of its molecular-scale structure which includes

adjustable length nanometer scale molecular film and abil-

ity to efficiently self-assemble56 DNA has been observed

to exhibit electrical features such as an insulator78

semiconductor910 conductivity11 and proximity-induced

superconductor12 There are generally two conduction meth-

ods hopping and tunneling suggested to describe the electri-

cal properties through DNA1314 Also there are many

factors that affect electrical characterization and interface

features of the device such as thickness15 temperature16

magnetic field17 and radiation1819

DNA is one of the most important organic materials that

have been used for manufacture of a number of devices16

Gahwiler et al using a 50 lm of DNA film to study the con-

ductivity induced by X-ray showed that the current grows

linearly with the exposure-rate without saturating and a short

time constant20 Pablo et al observed fast contamination

through Scanning Force Microscopy (SFM) images and

dramatic influence in the measured conductivity when irradi-

ating DNA samples in a vacuum through a low-energy elec-

tron (LEE) beam21 Henderson et al exposed anthraquinone

derivative to UV light to create a radical cation on the GC

pair attached to the quinone The cation can thereby travel

down the length of DNA wherever there are GG sequences

in some places The position of the charge can be revealed as

strand scission at these sites by treatment of piperidine This

yields an exponential reliance of the charge transfer up to

about 18 nm of DNA length with a very large decay

length22 Keller et al observed that the LEEs have an essen-

tial role in nanolithography atmospheric chemistry and

DNA radiation damage is supposed to have strong implica-

tions for the plan of novel radio-sensitizing agents for cancer

therapy23 However creation of reactive radicals in the close

a)Authors to whom correspondence should be addressed Electronic

addresses hassankirkuklygmailcom and vengadeshpumedumy Tel

thorn6 016 2639762

0021-89792015118(11)1145027$3000 VC 2015 AIP Publishing LLC118 114502-1

JOURNAL OF APPLIED PHYSICS 118 114502 (2015)


10318017 On Wed 30 Sep 2015 023845

area of the DNA lead to secondary source of DNA radiation

damage24

In our present study of the effect of alpha (a) radiation

on DNA we used mushroom-based DNA layer on aluminum

(Al) to fabricate AlDNAAl Schottky diode structures To

the best of our knowledge no studies on the effects of alpha

radiation on similar structures have ever been reported

before in real time The aim of this study is therefore to fab-

ricate a DNA-based metalDNAmetal diode for potential

utilization as an alpha particle detectorsensor Current-volt-

age (I-V) measurements were then performed to analyze the

electrical properties of the DNA-based MDM diode as the

radiation sensitive material

MATERIALS AND METHODS

Preparation of DNA solution

A simple preparation procedure of mushroom DNA

extracted from the colonies of fruiting bodies was used for

Polymerase Chain Reaction (PCR) amplification The proce-

dure starts with the collection of minute quantities of myce-

lium (01ndash10 g) from a colony of the fruiting body (Stipe) of

a mushroom species using a sterilized tweezer Standard

procedures according to Hibbett25 were further employed to

yield pure DNA samples prior to the PCR process The DNA

of all samples was amplified by PCR (PTC-100TM MJ

Research Inc Ramsey MN USA) using universal primers

ITS1 forward (50-TCC GTA GGTGA AC CTGCGG-30) and

ITS4 reverse (50-TCCTCCGCTT ATT GATATGC-30)Amplification reactions were performed in a total volume of

500 ll containing 10 PCR buffer 40 ll dNTP mix 25 ll

25 ll of each primer 10 ll of Taq polymerase (Cosmo

Seongnam-si Gyeonggi-do Korea) 40 ll of genomic

(Template DNA) and 260 ll of sterilized distilled water

PCR amplification was carried-out in 30 cycles at 94 C for

30 min and denatured at 50 C for 60 min followed by

annealing at 72 C for an extension of 1 min Initial denatur-

ing at 95 C was extended to 5 min and the final extension

was at 72 C for 5 min reaching stable conditions at 4 C2627

Fabrication of the AlDNAAl sensor

Glass slides cleaned for 15 min using deionized water

(182 MX cm Barnstead Nanopure II water system Lake

Balboa CA USA) in an ultrasonic cleaner and later dried in

a dust free environment were utilized as the substrate Thin

films of Al (thickness 325 nm) were deposited on the glass

substrate using an Edward Auto 306 vacuum coater with a

diffusion pumping system (Edward Auto 306 West Sussex

United Kingdom) and Al metal wire (Kurt J Lesker Hudson

Valley PA USA) of 99999 purity While depositing the

Al thin film pressure inside the chamber was kept at 105

mbar whereas the deposition rate was maintained at

01 nms The gap between the electrodes was 30 lm while

the length of the gap was 25 mm after which the formation

of the organic DNA layer was carried-out by using a micro

syringe (Hamilton micro syringe concentration of DNA

180 ngll) containing 10 ll pre-prepared DNA solution The

fabricated device was then kept in a 1K-class clean room

Sample irradiation by alpha particles was achieved using241Am with an activity of 150 nCurie and t12 of 457 years

(The Radiochemical Centre Amersham England) for peri-

ods of 2ndash40 min

We measured the thickness of the DNA layer using two

devices Ellipsometer and Profilermeter For the non-

radiated sample the thickness was measured at 100 nm The

thickness increased with the increase in the irradiation

time as there is an increase in the number of tracks and

therefore its roughness The value for the effective area is

1625 105 m2 while the distance of the source from the

DNA layer was maintained at 2 cm Cross-sectional view

and image of the AlDNAAL surface-type Schottky diode

are shown in Figure 1

RESULTS AND DISCUSSION

The forward and reverse bias I-V characteristics of the

AlDNAAl junctions at room temperature are given in

Figure 2(a) and I-V-T in Figure 2(b) As can be observed

the I-V characteristics of the device demonstrate a rectifying

behavior

Figure 2(a) demonstrates the relation between the I-V

showing good rectifying trend for the current Figure 2(b)

meanwhile shows the three-dimensional relationship

between I-V and irradiation time

According to the thermionic emission theory the I-V

characteristic of a diode is given by17

I frac14 Io expqV

nKT

1 exp

qV

KT

(1)

where Io frac14 AAT2 qUKT

(2)

where q is the elementary charge the applied voltage by V

and effective Richardson constant by symbol A and equal

to 120 Acm2 K2 for Al28 Symbol A meanwhile represents

the active diode area T the absolute temperature K the

Boltzmann constant n the ideality factor of a Schottky bar-

rier diode Ubo the zero bias barrier height and RS is the se-

ries resistance For values of Vgt 3kTq the ideality factor

from Equation (1) can be re-written as

FIG 1 Schematic diagram (left) and image (right) of the AlDNAAl sensor

(picture credit to Hassan Maktuff Jaber)

114502-2 Al-Tarsquoii Periasamy and Amin J Appl Phys 118 114502 (2015)


10318017 On Wed 30 Sep 2015 023845

n frac14 q

KT

dV

d ln I

(3)

The ideality factor determined from the slope of the linear

region of the forward bias (ln(I)-V) characteristic through

the relation in Equation (3) is a measure of conformity of

diode to pure thermionic emission2930 n equals to 1 for an

ideal diode but here it demonstrates higher values These

high values of n can be attributed to the presence of interfa-

cial thin film a huge distribution of low Schottky barrier

height (SBH) patches (or barrier inhomogeneity) rearrange-

ment of electrons and holes in the depletion regions and bias

dependence of voltage of SBH31 Figure 3 shows the ideality

factor fluctuations of AlDNAAl based junctions fabricated

in this work calculated using Equation (3)

For both the radiated and non-radiated samples the

linear region of the forward bias I-V plots indicate that the

effect of the series resistance in this region is not important

The value of the barrier height (U) of the AlDNAAl

Schottky diode was 07149 eV before irradiation Values

before and after irradiation (Table I) were calculated from

the y-axis intercepts of the semi log-forward bias I-V plots

using Equation (4) It should to be noted that U is the

connection potential barrier that exists at the interface

between inorganic and organic layers ie at the DNAAl

interface

U frac14 KT

qln

AAT2

Io

(4)

The values of series resistance are calculated from the junc-

tion resistance formula RS frac14 V=I from the I-V properties

of the diode The resistance RS versus voltage of the surface-

type Schottky diode is demonstrated in Figure 4 From the

figure it can be concluded that at low voltages (20 V) RS

values were the highest for non-radiated 30 and 4 min in

reducing order followed by the sample radiated for 2 min

However above 20 V the RS values become insignificant

At high currents there is always a deviation of the ideality

factor that has been obviously shown to rely on bulk series

resistance and the interface state density as one would

expect The lower the series resistance and the interface state

density the better is the range over which lnI(V) does in

reality yield a straight line The Schottky diode factors such

as the barrier height Ubo the series resistance Rs and the

ideality factor n were also determined using the technique

advanced by Cheung and Cheung32 The methodrsquos functions

can be written as

dV

d ln Ieth THORN frac14 IRS thornnKT

q (5)

H Ieth THORN frac14 V KT

q

ln

I

AAT2

(6)

Therefore

HethITHORN frac14 IRS thorn nUb (7)

Figures 5(a) and 5(b) show the experimental H(I) versus I

and dVd(lnI) versus I plots respectively for the AlDNAAl

Schottky diode at room temperature A plot of H(I) versus I

(Figure 5(a)) shows a straight line with intercept at y-axis

FIG 2 Graphs demonstrate the relationship between current and voltage I-

V-T for forward and reverse biases in real time

FIG 3 Profiles show the log I-V characteristics of AlDNAp-Si Schottky

diode at room temperature



10318017 On Wed 30 Sep 2015 023845

equal to nU U was obtained by substituting the n value from

Equation (5) and the data of the downward curvature region

in the forward bias I-V graph from Equation (7) The slope

of this plot also limits RS which can be utilized to check the

accuracy of Cheung and Cheungrsquos method From H(I) versus

I the U and RS values were measured and presented in

Table I Equation (5) gives a straight line for the data of the

downward curvature region in the forward bias I-V graph

RS was obtained from both the conventional and the

Cheung and Cheungrsquos models but the values calculated

using the former method were higher than the ones derived

from the latter one (Figure 6) Generally values of n

obtained from the dVd(ln I) versus I curve are higher than

that of the forward bias ln I versus V plot This can be attrib-

uted to the effect of the series resistance interface states and

voltage drop across interfacial layers33ndash35and radiation

effect36

Figure 7 displays the dual logarithmic plot of forward

bias I-V properties of the AlDNAAl junction The log(I)-

log(V) graphs clearly show the power law behavior of the I-

V curve Space-charge-limited current (SCLC) effecting the

diode and its charge transport can be shown through the

Ifrac14Vm rule where m is the slope of each region which

corresponds to ohmic and SCLC The m values of the region

shown in Table II portray three linear regions of the log(I)-

log(V) plot of the forward bias I-V properties Region (I)

shows an ohmic region while region (II) demonstrates the

presence of the SCLC mechanism controlled by the traps

TABLE I Values of ideality factor barrier height and series resistance

Irradiation

time (min)

Conventional thermionic emission model Cheung-Cheungrsquos method

n U (eV) RS (MX) n RS (MX) U (eV) RS (MX)

0 156814 07149 2743 34109 0180 06983 09694

2 113911 07286 1896 30233 0130 07528 06301

4 264286 07367 03637 42636 0028 06124 00144

6 223706 06704 1547 29457 0110 06124 04828

8 123710 07129 06362 35271 0048 06867 02560

10 229404 07009 1413 34109 0100 06114 106804

20 145968 08481 1764 33333 0120 06945 05132

30 131230 07680 1845 22868 0140 06650 06444

40 241728 07164 04665 26744 0300 06265 155188

FIG 4 Plot of the bias-dependent resistance Rifrac14 dVdI versus applied volt-

age for AlDNAAl junction

FIG 5 H(I) and dVd(ln I) versus I graphs obtained from forward bias I-V

characteristics of AlDNAAl Schottky junction diode



10318017 On Wed 30 Sep 2015 023845

The second region of this graph having a slope of between

(247 and 52) up to a transition voltage of about 27 V is

similar to the SCLC with the exponential distribution of traps

in the band gap of the organic material The third region of

double logarithmic forward bias curve has a slope value of

between (11 and 25) except for the sample with 20 min of

radiation This region shows that at higher voltages the slope

of the curve decreases because the device approaches the

trap filled limit

In this work the n values demonstrated greater than unity

values when operated in the voltage range between 1 and

thorn1 V37 However when operated between 6 and thorn6 V

high values of n gives rise to a wide distribution of low bar-

rier height Schottky diodes and interfacial thin layer38 This

is due to an increase of defect density at the interface with

irradiation or lateral inhomogeneous barrier height39ndash41 In

this aspect the effects of alpha particle with higher mass

(4mp) and charge (thorn2e) compared to an electron become

greater than that of the electron and gamma rays (massless)42

At low doses the ideality factor drops dramatically

which demonstrates the hypersensitivity phenomena of the

DNA (Figure 8) and its self-protection This phenomenon is

similar to the behavior observed between survival curve and

dosage43ndash45 Schottky barrier height on the other hand has an

increased proportionality in relationship with the ideality

factor as shown in Figure 8 This may arise due to the DNA

oligonucleotides ability to resist the alpha radiation as dem-

onstrated by Figure 8 And the ideality factor from Cheung-

Cheungrsquos method registers lower values compared to the

conventional method On the other hand the Ub value from

conventional method becomes higher than Ub from Cheung-

Cheungrsquos method The hypersensitivity phenomenon was

observed in that the cells obtain some resistance after irradia-

tion to about 05 Gy where the typical response exhibited

an exponential form of the survival curve It begins to rise at

about 05 Gy to an upper survival limit as the irradiation

dose rises before eventually decreasing in a normal manner

as observed earlier45ndash48

Figure 9 demonstrates that the Richardson constant is

very sensitive to the radiation effect Richardson constant

FIG 6 Diagrams demonstrate the relationship between RS and alpha radia-

tion time

FIG 7 Double logarithmic plots of the AlDNAAl junctions

TABLE II Values of (m) for regions (I) (II) and (III) of the power law Al

DNAAl

Irradiation time

(min)

AlDNAAl junction (slope gradient m)

Region (I) Region (II) Region (III)

0 088799 503999 251623

2 053536 473327 168588

4 012278 52034 173042

6 061435 327404 180156

8 035643 453009 126685

10 084715 247782 158914

20 064404 383097 069162

30 080862 465787 102202

40 065955 503193 111818 FIG 8 Graphs demonstrate the relation between the ideality factor and bar-

rier height by irradiation time



10318017 On Wed 30 Sep 2015 023845

was measured from the I-V curve and it increases with irra-

diation time The ionizing radiation process leads to energy

sedimentation in the metal appearing as thermal heat and

changing the material properties42 The work function of the

metalsemiconductor junction changes which provides suffi-

cient energy for the charge carriers to get over the binding

potential Increasing number of alpha particles tracks also

leads to increase in the number of holes thereby increasing

the effective mass which causes a lower rate of carriers to

break through the potential barrier reducing the current

Due to the excitation of the material by ionizing radia-

tion such as by alpha particles a huge number of excited

atoms are produced along its path thereby increasing the

number of electrons Further a decrease in the number of

electrons was observed as a result of collisions between the

MDM electrodes and the increase in resistance due to the

number of traps in DNA preventing internal charge move-

ment and hence increases the electrical resistance4950 This

results in an increase in the barrier heights as in Table III

followed by a decline in the current

In these experiments we measured the current with

increasing irradiation for all the samples for the same time

periods Electrical field increases due to the I-V response

through the circuit and the alpha particle charge incident on

the DNA layer which increases the number of electron trans-

fer from the valance to conductance band This can be

explained as after the traversal of the alpha particles to the

DNA layer a large number of excited atoms along the alpha

particles tracks were produced thereby the holes left in the

valence band and electrons in the conduction band could be

important in increasing the electrical conductivity of both

semiconductors and insulating materials This phenomenon

is well known as the radiation-induced conductivity Thus

electron-hole pairs are created (electron in the conduction

and hole in the valence band) due to this irradiation event

On the other hand irradiation also creates secondary electron

charge carriers which affects the electrical properties The

relaxation time in semiconductors such as in the DNA

strands becomes longer than compared to metals causing

more permanent damage42

CONCLUSIONS

In this study we fabricated surface type AlDNAAl

Schottky barrier diodes and generated I-V measurements

upon exposure to increasing dosage of alpha radiation at room

temperature The effects of hypersensitivity of DNA to alpha

irradiation need to be further addressed as a probable comple-

mentary cause for changes in the ideality factors and series re-

sistance The values of the ideality factors series resistances

and barrier heights were calculated from the measured non-

ideal I-V curves conventional and Cheung and Cheung tech-

niques From the conventional method the calculated U value

for non-radiated DNA films was 07149 eV which increased

to 07367 eV after 4 min of radiation Furthermore barrier

height values were observed to increase after 20 30 and

40 min of radiation except for 6 8 and 10 min which regis-

tered a decrease of about 067 071 and 070 respectively

This study shows that conventional thermionic emission

model could be the best and most practical for estimating the

diode parameters including the effect of series resistance of

the AlDNAAl Schottky diode structures under consideration

The increase in the electrical resistance may be due to the

drop in the forward current at high voltages whereas the drop

in barrier height values is as a result of the growth of the

reverse current28 The effects of hypersensitivity of DNA to

alpha irradiation need to be further addressed as a probable

complementary cause for changes in the ideality factors and

series resistance Nevertheless the various parameters studied

in this work may well demonstrate the potential application of

the fabricated AlDNAAl junction type sensor for sensing

alpha particles

ACKNOWLEDGMENTS

Financial assistance provided by the FRGS (FP004-

2013A) UMRG (RG321-15AFR) and (PG202-2014B)

grants is greatly appreciated The first author would also like

to thank the Ministry of Higher Education and Scientific

Research of Iraq for the financial assistance provided for his

PhD study

HMJA-T and VP conceived and designed the

experiments HMJA-T performed the experiments

FIG 9 Irradiation time dependent Richardson constant for the MDM

structure

TABLE III Barrier height and Richardson constant (A) against irradiation

time in AlDNAAl (U) structures

Irradiation

time (min)

Richardson constant

A (A cm2 K2)

Barrier height

U (eV)

0 11857569 07149

2 11832802 07286

4 11812141 07367

6 11849909 06704

8 11819823 07129

10 1184912 07009

20 11804117 08481

30 11818911 07680

40 1182611 07164



10318017 On Wed 30 Sep 2015 023845

HMJA-T and VP analyzed the data VP and HMJA-

T contributed reagentsmaterialsanalysis tools HMJA-T

and VP wrote the paper

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10318017 On Wed 30 Sep 2015 023845

Detection of alpha particles using DNAAl Schottky junctions

Hassan Maktuff Jaber Al-Tarsquoii12a) Vengadesh Periasamy1a) and Yusoff Mohd Amin3

1Low Dimensional Materials Research Centre (LDMRC) 50603 Kuala Lumpur Malaysia2Department of Physics Faculty of Science University of Al-Muthana Al-Muthana 66001 Iraq3Department of Physics Faculty of Science University of Malaya 50603 Kuala Lumpur Malaysia

(Received 9 June 2015 accepted 30 August 2015 published online 16 September 2015)

Deoxyribonucleic acid or DNA can be utilized in an organic-metallic rectifying structure to detect

radiation especially alpha particles This has become much more important in recent years due to

crucial environmental detection needs in both peace and war In this work we fabricated an alumi-

num (Al)DNAAl structure and generated currentndashvoltage characteristics upon exposure to alpha

radiation Two models were utilized to investigate these current profiles the standard conventional

thermionic emission model and Cheung and Cheungrsquos method Using these models the barrier

height Richardson constant ideality factor and series resistance of the metal-DNA-metal structure

were analyzed in real time The barrier height U value calculated using the conventional method

for non-radiated structure was 07149 eV increasing to 07367 eV after 4 min of radiation Barrier

height values were observed to increase after 20 30 and 40 min of radiation except for 6 8 and

10 min which registered a decrease of about 067 eV This was in comparison using Cheung and

Cheungrsquos method which registered 06983 eV and 07528 eV for the non-radiated and 2 min of

radiation respectively The barrier height values meanwhile were observed to decrease after 4

(061 eV) to 40 min (06945 eV) The study shows that conventional thermionic emission model

could be practically utilized for estimating the diode parameters including the effect of series resist-

ance These changes in the electronic properties of the AlDNAAl junctions could therefore be uti-

lized in the manufacture of sensitive alpha particle sensors VC 2015 AIP Publishing LLC

[httpdxdoiorg10106314930888]

INTRODUCTION

Radiation sensors are not only required in diagnostics

and imaging technologies but are also increasingly utilized

in medicine space technology industry and research12

These applications generally encompass various aspects such

as security imaging quality control treatment and safety

Sensors are devices that produce significant variation to a

well-known input stimulus This motivation can be a physi-

cal impetus similar to temperature or pressure or a concentra-

tion of a specific chemical or biochemical material3

The radiation effect on the active material utilized within

the sensing device therefore determines the function of the

sensor being developed4

There are six classes of sensors typically differentiated

by the energy transduced in the sensor These are thermal

optical electronic mechanical magnetic and electrochemi-

cal sensors3 DNA molecules are described as a double

stranded negatively charged polymer These negatively

charged molecules can modify the interfacial electronic

states of metalsilicon semiconductor structures DNA in

recent years has been a material of choice due to its proper-

ties in terms of its molecular-scale structure which includes

adjustable length nanometer scale molecular film and abil-

ity to efficiently self-assemble56 DNA has been observed

to exhibit electrical features such as an insulator78

semiconductor910 conductivity11 and proximity-induced

superconductor12 There are generally two conduction meth-

ods hopping and tunneling suggested to describe the electri-

cal properties through DNA1314 Also there are many

factors that affect electrical characterization and interface

features of the device such as thickness15 temperature16

magnetic field17 and radiation1819

DNA is one of the most important organic materials that

have been used for manufacture of a number of devices16

Gahwiler et al using a 50 lm of DNA film to study the con-

ductivity induced by X-ray showed that the current grows

linearly with the exposure-rate without saturating and a short

time constant20 Pablo et al observed fast contamination

through Scanning Force Microscopy (SFM) images and

dramatic influence in the measured conductivity when irradi-

ating DNA samples in a vacuum through a low-energy elec-

tron (LEE) beam21 Henderson et al exposed anthraquinone

derivative to UV light to create a radical cation on the GC

pair attached to the quinone The cation can thereby travel

down the length of DNA wherever there are GG sequences

in some places The position of the charge can be revealed as

strand scission at these sites by treatment of piperidine This

yields an exponential reliance of the charge transfer up to

about 18 nm of DNA length with a very large decay

length22 Keller et al observed that the LEEs have an essen-

tial role in nanolithography atmospheric chemistry and

DNA radiation damage is supposed to have strong implica-

tions for the plan of novel radio-sensitizing agents for cancer

therapy23 However creation of reactive radicals in the close

a)Authors to whom correspondence should be addressed Electronic

addresses hassankirkuklygmailcom and vengadeshpumedumy Tel

thorn6 016 2639762

0021-89792015118(11)1145027$3000 VC 2015 AIP Publishing LLC118 114502-1

JOURNAL OF APPLIED PHYSICS 118 114502 (2015)


10318017 On Wed 30 Sep 2015 023845


damage24























































ods of 2ndash40 min
















behavior







I frac14 Io expqV

nKT

1 exp

qV

KT

(1)


(2)













10318017 On Wed 30 Sep 2015 023845

n frac14 q

KT

dV

d ln I

(3)























interface

U frac14 KT

qln

AAT2

Io

(4)


















can be written as

dV


q (5)


q

ln

I

AAT2

(6)

Therefore












10318017 On Wed 30 Sep 2015 023845

















effect36













Irradiation

time (min)



0 156814 07149 2743 34109 0180 06983 09694

2 113911 07286 1896 30233 0130 07528 06301

4 264286 07367 03637 42636 0028 06124 00144

6 223706 06704 1547 29457 0110 06124 04828

8 123710 07129 06362 35271 0048 06867 02560

10 229404 07009 1413 34109 0100 06114 106804

20 145968 08481 1764 33333 0120 06945 05132

30 131230 07680 1845 22868 0140 06650 06444

40 241728 07164 04665 26744 0300 06265 155188







10318017 On Wed 30 Sep 2015 023845









trap filled limit

































tion time



DNAAl

Irradiation time

(min)



0 088799 503999 251623

2 053536 473327 168588

4 012278 52034 173042

6 061435 327404 180156

8 035643 453009 126685

10 084715 247782 158914

20 064404 383097 069162

30 080862 465787 102202





10318017 On Wed 30 Sep 2015 023845









































CONCLUSIONS





























alpha particles

ACKNOWLEDGMENTS






PhD study




structure



Irradiation

time (min)

Richardson constant

A (A cm2 K2)

Barrier height

U (eV)

0 11857569 07149

2 11832802 07286

4 11812141 07367

6 11849909 06704

8 11819823 07129

10 1184912 07009

20 11804117 08481

30 11818911 07680

40 1182611 07164



10318017 On Wed 30 Sep 2015 023845






















ACS Nano 6 4392 (2012)























10318017 On Wed 30 Sep 2015 023845


damage24























































ods of 2ndash40 min
















behavior







I frac14 Io expqV

nKT

1 exp

qV

KT

(1)


(2)













10318017 On Wed 30 Sep 2015 023845

n frac14 q

KT

dV

d ln I

(3)























interface

U frac14 KT

qln

AAT2

Io

(4)


















can be written as

dV


q (5)


q

ln

I

AAT2

(6)

Therefore












10318017 On Wed 30 Sep 2015 023845

















effect36













Irradiation

time (min)



0 156814 07149 2743 34109 0180 06983 09694

2 113911 07286 1896 30233 0130 07528 06301

4 264286 07367 03637 42636 0028 06124 00144

6 223706 06704 1547 29457 0110 06124 04828

8 123710 07129 06362 35271 0048 06867 02560

10 229404 07009 1413 34109 0100 06114 106804

20 145968 08481 1764 33333 0120 06945 05132

30 131230 07680 1845 22868 0140 06650 06444

40 241728 07164 04665 26744 0300 06265 155188







10318017 On Wed 30 Sep 2015 023845









trap filled limit

































tion time



DNAAl

Irradiation time

(min)



0 088799 503999 251623

2 053536 473327 168588

4 012278 52034 173042

6 061435 327404 180156

8 035643 453009 126685

10 084715 247782 158914

20 064404 383097 069162

30 080862 465787 102202





10318017 On Wed 30 Sep 2015 023845









































CONCLUSIONS





























alpha particles

ACKNOWLEDGMENTS






PhD study




structure



Irradiation

time (min)

Richardson constant

A (A cm2 K2)

Barrier height

U (eV)

0 11857569 07149

2 11832802 07286

4 11812141 07367

6 11849909 06704

8 11819823 07129

10 1184912 07009

20 11804117 08481

30 11818911 07680

40 1182611 07164



10318017 On Wed 30 Sep 2015 023845






















ACS Nano 6 4392 (2012)























10318017 On Wed 30 Sep 2015 023845

n frac14 q

KT

dV

d ln I

(3)























interface

U frac14 KT

qln

AAT2

Io

(4)


















can be written as

dV


q (5)


q

ln

I

AAT2

(6)

Therefore












10318017 On Wed 30 Sep 2015 023845

















effect36













Irradiation

time (min)



0 156814 07149 2743 34109 0180 06983 09694

2 113911 07286 1896 30233 0130 07528 06301

4 264286 07367 03637 42636 0028 06124 00144

6 223706 06704 1547 29457 0110 06124 04828

8 123710 07129 06362 35271 0048 06867 02560

10 229404 07009 1413 34109 0100 06114 106804

20 145968 08481 1764 33333 0120 06945 05132

30 131230 07680 1845 22868 0140 06650 06444

40 241728 07164 04665 26744 0300 06265 155188







10318017 On Wed 30 Sep 2015 023845









trap filled limit

































tion time



DNAAl

Irradiation time

(min)



0 088799 503999 251623

2 053536 473327 168588

4 012278 52034 173042

6 061435 327404 180156

8 035643 453009 126685

10 084715 247782 158914

20 064404 383097 069162

30 080862 465787 102202





10318017 On Wed 30 Sep 2015 023845









































CONCLUSIONS





























alpha particles

ACKNOWLEDGMENTS






PhD study




structure



Irradiation

time (min)

Richardson constant

A (A cm2 K2)

Barrier height

U (eV)

0 11857569 07149

2 11832802 07286

4 11812141 07367

6 11849909 06704

8 11819823 07129

10 1184912 07009

20 11804117 08481

30 11818911 07680

40 1182611 07164



10318017 On Wed 30 Sep 2015 023845






















ACS Nano 6 4392 (2012)























10318017 On Wed 30 Sep 2015 023845

















effect36













Irradiation

time (min)



0 156814 07149 2743 34109 0180 06983 09694

2 113911 07286 1896 30233 0130 07528 06301

4 264286 07367 03637 42636 0028 06124 00144

6 223706 06704 1547 29457 0110 06124 04828

8 123710 07129 06362 35271 0048 06867 02560

10 229404 07009 1413 34109 0100 06114 106804

20 145968 08481 1764 33333 0120 06945 05132

30 131230 07680 1845 22868 0140 06650 06444

40 241728 07164 04665 26744 0300 06265 155188







10318017 On Wed 30 Sep 2015 023845









trap filled limit

































tion time



DNAAl

Irradiation time

(min)



0 088799 503999 251623

2 053536 473327 168588

4 012278 52034 173042

6 061435 327404 180156

8 035643 453009 126685

10 084715 247782 158914

20 064404 383097 069162

30 080862 465787 102202





10318017 On Wed 30 Sep 2015 023845









































CONCLUSIONS





























alpha particles

ACKNOWLEDGMENTS






PhD study




structure



Irradiation

time (min)

Richardson constant

A (A cm2 K2)

Barrier height

U (eV)

0 11857569 07149

2 11832802 07286

4 11812141 07367

6 11849909 06704

8 11819823 07129

10 1184912 07009

20 11804117 08481

30 11818911 07680

40 1182611 07164



10318017 On Wed 30 Sep 2015 023845






















ACS Nano 6 4392 (2012)























10318017 On Wed 30 Sep 2015 023845









trap filled limit

































tion time



DNAAl

Irradiation time

(min)



0 088799 503999 251623

2 053536 473327 168588

4 012278 52034 173042

6 061435 327404 180156

8 035643 453009 126685

10 084715 247782 158914

20 064404 383097 069162

30 080862 465787 102202





10318017 On Wed 30 Sep 2015 023845









































CONCLUSIONS





























alpha particles

ACKNOWLEDGMENTS






PhD study




structure



Irradiation

time (min)

Richardson constant

A (A cm2 K2)

Barrier height

U (eV)

0 11857569 07149

2 11832802 07286

4 11812141 07367

6 11849909 06704

8 11819823 07129

10 1184912 07009

20 11804117 08481

30 11818911 07680

40 1182611 07164



10318017 On Wed 30 Sep 2015 023845






















ACS Nano 6 4392 (2012)























10318017 On Wed 30 Sep 2015 023845









































CONCLUSIONS





























alpha particles

ACKNOWLEDGMENTS






PhD study




structure



Irradiation

time (min)

Richardson constant

A (A cm2 K2)

Barrier height

U (eV)

0 11857569 07149

2 11832802 07286

4 11812141 07367

6 11849909 06704

8 11819823 07129

10 1184912 07009

20 11804117 08481

30 11818911 07680

40 1182611 07164



10318017 On Wed 30 Sep 2015 023845






















ACS Nano 6 4392 (2012)























10318017 On Wed 30 Sep 2015 023845






















ACS Nano 6 4392 (2012)























10318017 On Wed 30 Sep 2015 023845

detection of alpha particles using dna/al schottky … · detection of alpha particles using dna/al...

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