Review on the Production and Synthesis of Nanosized SnO2

S.A. Papargyri3, D. N.Tsipas3, D.A. Papargyris2 , A.I. Botis1

and A.D. Papargyris1

1 Technological & Educational Institute of Larissa, General Department of Applied Sciences,

Materials Laboratory, Larissa 41110, Larissa, Greece 2 UMIST, Materials Centre, UK

3 Aristotle University, Polytechnic School, Mechanical Engineering Department, Thessaloniki,

Greece Keywords: Tin Dioxide, SnO2, nanomaterials, synthesis, semiconducting materials.

Abstract. Tin dioxide is a wide band semiconductor, with interesting chemical physical and

mechanical properties, used in a variety of industrial, domestic, medical and agricultural

applications, including gas detectors, transparent conductors, solar cells, anti-static films,

nanoelectronic devices etc. The variety of nanosized SnO2 production methods in the form of

powders or layers (e.g. solid state, sol-gel, sputtering, laser ablation, template, solution precipitation,

precursor oxidation, CVD, PVD, etc) are discussed.

Introduction

Tin dioxide is an n-type wide band semiconductor ( Eg=3.6 eV at 300 K), with interesting chemical,

physical and mechanical properties, used in a variety of domestic, industrial, agricultural and

medical applications, including gas detectors (for H2, O2, CO, CO2, NOx, H2S etc), nanoelectronic

devices, conductors, transistors, dye-based solar cells, transparent conducting electrodes, antistatic

films, etc. Therefore there is great interest in its production {e.g. [1,2]}. Tin oxide is produced as

bulk powder, layers or films in the forms, including nanorods, nanowires, nanobelts, nanoribbons

and nanotubes. The formation of doped tin oxide with different dopants using various methods, has

been used to improve, optical properties like luminescence, selectivity in gas mixtures, sensitivity

and reducing degradation of performance with time and other properties.

Production methods

Production methods for SnO2 production are divided to wet or dry processes depending on the form

of the starting materials

A. Dry Processes.

Dry processes for the bulk synthesis of nanowires can be carried out using a variety of procedures,

including thermal evaporation, vapour-liquid-solid (VLS), solution, template, laser, arc-discharge

and other methods (e.g. [3-9]. The vapour liquid solid (VLS) technique has been also used for the

synthesis of SnO2 whiskers [10]. Tin dioxide produced as a layer by dry processes involve:

sputtering from a metallic target followed by oxidation [11], sputtering from a tin oxide target

under different oxygen partial pressures [12,13], chemical vapour deposition (CVD) [14], or plasma

enchanced CVD (PECVD) [15]. An inexpensive method of tin oxide nanoparticles production with

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sizes from 3 to 15 nm, is to use the one step solid-state reaction synthesis, at ambient conditions,

using SnCl4 and KOH as starting materials [16]. The solid state reaction can be written as:

SnCl4·5H2O(s)+4KOH(s) → 4KCl(s) + SnO2·H2O(s) + 6H2O(g)

Tin oxide films have been prepared by physical vapour deposition (PVD) of Sn followed by thermal

oxidation and by spray pyrolysis of SnCl4 or SnCl4·5H2O mixed with CH3OH [17]. Highly

conducting and transparent thin films of undoped tin oxide (SnO2) have been prepared on unheated

substrates by RF magnetron sputtering under an applied external DC magnetic field [18].

With regard to the reaction temperature, the production of SnO2 is divided into high (≥1000oC)

medium (~800oC) and low ( <1000

oC) temperature methods.

High temperature synthesis of rutile and orthorhombic crystalline tin oxide nanowires, nanoribbons

and nanotubes has been achieved through the oxidation of SnO/Sn and SnO based mixtures in a

double concentric alumina tube arrangement heated to 1050-1150oC [19,20]. The synthesis of one-

dimensional (1D) nanostructures (nanowires, nanobelts and nanodendrites) has also been reported

using a gas reaction route:

Sn+O2 → SnO2

at 900oC in a horizontal tube furnace [21]. High yield SnO2 nanobelts and nanowires were also

produced by the carbothermal reaction of SnO2 with graphite at 1150°C without a metallic catalyst

and vacuum conditions [22]:

2SnO2(s)+C(s)→ 2SnO(v)+CO2(v)

SnO(v) → SnO2(s) + Sn(l)

2Sn(l) + O2(v) → 2SnO (v)

Medium temperature synthesis of SnO2 nanobelts was reported as being achieved by heating an

alumina boat filled with pure Sn powder, under a flowing Argon atmosphere in a horizontal tube at

a temperature of 800 ◦C for 2 hours and then cooling [23,24].

Low temperature synthesis of bulk quantities of SnO2 in the form of nanowires, dominated by a

self-catalytic VLS mechanism (>300oC), has been reported recently [25]:

2SnO(g) → Sn(l) + SnO2(s)

SnO2(s) ↔ SnO(g) + 1/2 O2 (reversible reaction)

These reactions take place in horizontal furnace under vacuum, and the nano-oxide is formed as an

ivory-yellow cotton-wool like product over the source SnO. It was suggested that the formed Sn

probably serves as a liquid nucleus for VLS growth of the SnO2 nanowires. These as-synthesized

SnO2 nanowires were single crystals with [301] growth axis and diameters ranging from 10 to 190

nm and lengths extending to tens of micrometers. Also under mild conditions (700oC), rectangular

SnO2 nanowires with widths ranging between 10-50 nm, have been produced by the active carbon

reaction with fine SnO2 [26]. During the thermal evaporation process, at 700oC, the metastable SnO

in a gaseous state is decomposed to SnO2 :

C(s)+SnO2(s)→SnO(g)+CO(g)

CO(g)+ SnO2(s) → SnO(g) + CO2(g).

2SnO(g) → Sn (l)+SnO2(s)

58 From Nanopowders to Functional Materials

Thin films of nanocrystalline SnO2 with grain sizes below 6.8 nm, applicable to optoelectronics (e.g.

solar cells, gas sensors etc) have been produced on p-InSb (111) substrates by radio-frequency

magnetron sputtering at low temperature [27].

The physical vapour deposition ( PVD) route was used for synthesis of palladium doped tin oxide

on a soda-lime glass substrate, via magnetron sputtering, from a SnO2 target and evaporation of a

surface thin film of palladium [28]. The resulting doped tin oxide had higher sensitivity. Another

method was published quite recently for producing nanosized tin dioxide in the form of layers. It

was reported that SnO2 particles deposited onto silicon nitride coated microelectronic platforms can

be used in gas sensors based on metal oxide semiconductors. The process involved oxidation at

moderate temperature (600oC ) of Sn/SnOx nanocomposite particles formed by the decomposition of

an organometallic precursor [Sn(NMe2)2]2 in a controlled water/anisol mixture [29]. It was stated

that doping in the surface of preformed tin dioxide in the sensors with palladium, achieved by co-

decomposition of organometallic precursors, or by deposition of palladium, improves their

sensitivity for CO sensing.

B. Wet processes.

These methods involve production of nanorods, via a redox reaction from a microemulsion system

containing cyclohexane , SnCl4, KBH4 and NaCl, followed by annealing at 780-1000oC [30]. The

reduction of Sn4+

with BH-4 produces a precipitate of black SnB, which further reduces to metallic

Sn, which is then oxidised at higher temperatures to SnO and finally to SnO2:

4Sn4+

+ 16BH-4 + 36H2O → 4SnB + 12B(OH)3 + 48H2

4SnB + 3O2 → 4Sn+2B2O3

4Sn + 2O2 → 4SnO + 2O2 → 4SnO2

Nanorods were also produced by using inverse microemulsion to synthesize a precursor from a

mixture of NaCl, Na2CO3, SnCl4 followed by calcination at 780-820oC [31]. Recent production

methods reported include, a new low temperature (160oC) hydrothermal process, using SnCl4,

NaOH and cetyltrimethyl ammonium bromide as a surfactant [32], and a high yield, >75%,

microemulsion technique, resulting in rutile structure nanorods, produced by annealing a nanoscale

microemulsion precursor in a molten salt flux and surfactant at 780-810oC [33].

Hydrothermal synthesis at 130-250oC for 2-5 hours followed by annealing at 500

oC was used to

produce SnO2 powder from different precursors based on stannic acid or chloride using NH4OH as

the precipitant [34]. SnO2 semiconducting spherical nanoparticles 3-5 nm in size, were synthesized

by sonochemical synthesis (ultrasonic irradiation) initially at room temperature and at 80oC after 2

hours in an aqueous solution of SnCl4 and azodicarbonamide [35]. Sol-gel methods are popular

[36-43] and result in bulk materials with or without a nanocrystalline structure. Nanoparticles of

tin oxide have been synthesized by a simple sol–gel method using SnCl4 as the starting material and

adding NH4OH dropwise [44]. Alternatively, from a water-in-oil microemulsions [45], or by

adding ΝΗ4ΟΗ to an aqueous solution of SnCl4, followed by washing in bi-distilled water to

remove the chloride and calcination for 8 hours at 250 and 1000oC [46].

The template technique also has been used for tin oxide nano-production. An inexpensive one step

synthesis of uniform crystalline nanoparticles (15 nm) has been reported, using SnCl4 or SnCl2 as

the basic material and an amphiphilic triblock copolymer as a template [47].

Solid State Phenomena Vol. 106 59

The sol-gel method was used to produce nanosized semiconductor crystalline tin oxide doped with

dysprosium ions ( Dy3+

) particles with diameters of about 2.6 nm [48]. Aqueous ammonia solution

was added dropwise to an aqueous solution of hydrous tin chloride, SnCl4.5H2O, with small

amounts of dysprosium nitrite (Dy(NO3)3. The reaction produces an opal like gel which was

transformed to nanoparticles after cleaning and drying, at 80oC, and heat treatment at temperatures

between 400 and 600oC.

The co-precipitation method was used to form vanadium pentoxide, V2O5, doped tin oxide. (49). In

this method an ethanol solution of vanadium oxytrichloride (VOCl3) with NH4OH was added to tin

chloride (SnCl4) containing PEG as surfactant and the resulting precipitate was dried to form a

precursor (SnO3H2). Calcination produced 5.2 to 6.5 nm nanocrystalline V2O5 doped tin oxide:

SnO3H2 C500o

→ SnO2 + H2O

A precursor method was used to synthesise Sb-doped SnO2 thin films. An aqueous tin citrate

solution, prepared from SnCl2.2H2O and citric acid, was mixed with antimony oxide (Sb2O3) and

polymerization was started by adding ethylene glycol, followed by heat treatment at 300-550oC [50].

Discussion

Tin oxide nanoparticles can be produced, as nanorods, nanowires, nanobelts, and nanoribbons.

The methods used for production can be categorised as dry or wet and as high (~1000oC), medium

(~800oC) or low ( <700

oC) temperature. The techniques used include, thermal evaporation, sol-gel,

vapour-liquid-solid (VLS), CVD, PCV, solution, template, laser, arc-discharge and others.

The starting compounds and processes, in tin oxide production, usually are:

(a) a tin salt (SnCl4) reacting with:

(1) NH4OH or KOH as precipitants in hydrothermal synthesis; with or without

surfactant, sol-gel synthesis, or microemulsion,

(2) KBH4 in a redox reaction followed by annealing and oxidation, or,

(3) NaCl and Na2CO3 in inverse microemulsion followed by calcination,

(4) KBH4 and NaCl in microemulsion system containing cyclohexane and

annealing in a molten salt flux and surfactant,

(5) azodicarbonamide in sonochemical synthesis

(6) amphiphilic triblock copolymer as a template

(7) mixed with CH3OH followed by pyrolysis

(b) tin metal or a mixture of tin with tin oxide ( sputtering of Sn metal, gas phase reaction of

Sn, reaction of SnO/Sn and SnO, or of Sn/SnOx (formed through decomposition of an

organometallic precursor)

(c) elemental tin :

(1) in RF magnetron sputtered,

(2) deposited by PVD

d) tin oxide:

(1) in sputtering,

(2) in carbothermal reaction with graphite

(3) in self catalytic oxidation,

(4) in Pd doped SnO2 codeposited from an organometallic precursor

(e) stannic acid in hydrothermal synthesis

60 From Nanopowders to Functional Materials

The main problems with nanosized SnO2 production are the complexity of the processes and the

usually required high temperature which results in large grain sizes [9]. In many cases e.g. gas

sensing, the lack of crystalline purity is a great disadvantage, since gas detection applications require

perfect control of crystallinity and crystallite sizes near the grain size.

Other production methods (e.g. laser ablation, CVD, spray pyrolysis) show similar problems due to

coalescence during sintering which results in an increase of the mean grain size [51]. The particle

size of nanosized tin oxide is most important. As the particle size of the semiconductor particles is

reduced, the band gap increases and the edges of the bands split into discrete energy levels. The

smaller the particle size the higher is the sensitivity and the better the stability and the baseline drift

[52,53]. Doping of SnO2 is a promising way to obtain enhancement of the optical properties.

Conclusion

Synthesis of nanosized SnO2 in the form of powders, layers, films of various shapes can be achieved

by various methods including sol–gel, sputtering, precursor oxidation, CVD, PVD, solid state

reactions etc. The main quality problems with the majority of the wet production methods are the

complexity of process control and the lack of purity with respect to crystallinity. On the other hand

dry processes give high yields and there is no presence of organic matter, but they require complex

apparatus, high production temperatures and produce large grain size products.

The main targets in the production of nanosized tin oxide, are the development of new simple

production methods at low temperatures, giving smaller particle sizes, improved control of surface

mophology and crystallinity and, where applicable, incorporating new dopants in order to increase,

selectivity, sensitivity and stability, etc.. The methods include the use of redox reaction in inverse

microemulsion systems, template using copolymers, solid state processes with active carbon and

doping of SnO2 with V2O5 and Dy3+ and other dopants.

References

1. M. Zheng et al: Chem. Mater.Vol 13,11(2001), p. 3859.

2. M.S.Arnold, P. Avouris , Z.W. Pan, Z.L. Wang, J. Phys. Chem. B. (Comm.),107,3, (2003)

p.659-663.

3. S. Iijima.: Nature 354 (1991), p. 56.

4.. Z.W. Pan, Z.R. Dai and Z.L. Wang. Science 291 (2001), p. 1947

5. .Seeger, P.K. Redlich and M. Rühle,: Adv. Mater. 12 (2000), p. 279.

6. D. P. Yu, C. S. Lee, I. Bello, X. S. Sun, Y. H. Tang, G. W. Zhou, Z. G. Bai, Z. Zhang and S. Q.

Feng, Solid Sate Commun, 105,6, (1998), p 403-407

7. .J.D. Holmes, K.P. Johnston, R.C. Doty and B.A. Korgel :Science, 87 (2000), p.1471.

8. A.M. Morales and C.M. Lieber:Science, 279 (1998), p. 208.

9. O.C. Monteiro and T. Trindade: J. Mater. Sci. Lett. 19 (2000), p. 859

10. M. Nagano: J. Crystal Growth 66 (1984), p.377.

11. V. Demarne and A. Grisel : Sensors and Actuators, B 15–16 (1993), p.63

12. G. Micocci, A. Serra, P. Siciliano, A. Tepore and Z. Ali-Adib, : Vacuum 47 (1996), p.1175

13. T.W. Capehart and S.C. Chang : J. Vac. Sci. Technol. 18 (1981), p. 393

14. L. Bruno, C. Pijolat and R. Lalauze: Sensors and Actuators, B 18–19 (1994), p.195

15. Y. Liu, W. Zhu, O.K. Tan, X. Yao and Y. Shen: J.Mater. Sci:Mater.Electron.7 (1996), p.279

16..F. Li , J.Xu, X.Yu, L.Chen, J.Zhu, Z.Yang and X.Xin, : Sensors and Actuators B: Chemical, 81,

2-3, (2002) p165-169

Solid State Phenomena Vol. 106 61

17 S.H. Park, Y.C. Son, W.S. Willis, S.L. Suib and K.E.Creasy:Chem. Mater. 10 (1998), p2389

18. T. Minami, H. Nanto and S. Takata : Jpn. J. Appl. Phys. 27 (1988), p.L287

19. Z.R. Dai, J.L. Gole, J.D. Stout, Z.L. Wang, :,J. Phys. Chem. B 106 (2002), p. 1274

20. X. S. Peng, L. D. Zhang, G. W. Meng, Y. T. Tian, Y. Lin, B. Y. Geng, and S. H. Sun,

J. Appl. Phys. 93 (2003), p. 1760-1763

21. J.K. Jian, X.L. Chen, W.J. Wang, L. Dai and Y.P. Xu: Appl. Phys. A 76 (2003), p.291

22. S.H. Sun, G W Meng, M G Zhang, X H An, G S Wu and L D Zhang , J.Phys.D: Appl. Phys. 37

(2004) p.409-412

23. S.H. Sun, G.W.Meng, Y.W. Wang , T.Gao , M.G.Zhang, Y.T.Tian , X.S.Peng X S and L.D.

Zhang L D, Applied Physics A: Materials Science & Processing (2003), 76(2), 287-289

24. E. Comini, G. Faglia, G. Sberveglieri, Zhengwei Pan, and Zhong L. Wang, Appl. Phys. Lett. 81

(2002), p.1869-1871

25. Y.Q.Chen, X.F. Cui, K. Zhang, D.Pan, S. Zhang, B. Wang and J. G. Hou, Chem. Physics Lett.,

Vol.369, 1-2, (2003) p.16-20

26. J. X. Wang et al: Solid State Comm., 130,1-2 (2004), p 89

27. T. W. Kim, D. U. Lee, J. H. Lee, D. C. Choo, and M. Jung: J. Appl. Phys. 90 (2001), p.175

28. S. Gupta, R. K. Roy, M.P.M. Pal Chowdhury and A. K. Pal, Vacuum, 75, 2 (2004) p.111

29. C.Nayral, E.Viala, V. Collière, P. Fau, F. Senocq, A.Maisonnat and B.Chaudret, Appl.Surface

Sci, Vol.164, 1-4, (2000) p.219-226.

30. Y Liu, C.Zheng, W.Wang, Y. Zhan and G. Wang: J. Crystal Growth, 233, 1-2 (2001), p. 8

31. Y.K. Liu, C.L. Zheng, W.Z.Wang, C.R. Yin, G.H Wang: Adv. Mater. 13 (2001), p.1883.

32. C. Guo, , M. Cao and C. Hu,, Inor. Chem. Communications. 7, 7 (2004), p 929

33. C. Xu, X. Zhaob, S. Liu & G. Wang, Solid State Comm.,125, 6 (2003) p.301.

34. D. S. Torkhov, A. A. Burukhin, B. R. Churagulov, M. N. Rumyantseva, and V. D. Maksimov ,

Inorganic Materials, 39,11 (2003), p.1158-1162

35. J. Zhu, Z. Lu, S. T. Aruna, D. Aurbach, and A.Gedanken,Chem. Mater, 12 (9), (2000) p. 2557

36. Q. Pan, X. Dong, J. Zhang and L. He, Wuji Cailiao Xuebao 12 (1997), p 494]

37. N. Yamazoe,:Sensors and Actuators, B 5 (1991), p.7

38. C. Xu, J. Tamaki, N. Miura and N. Yamazoe :Sensors and Actuators, B3 (1991), p. 147

39. M. Ocana, C.J. Serna and E. Matijevic:Colloid Polym. Sci. 273 (1995), p.681

40. A. Diéguez, A. Romano-Rodriguez, J.R. Morante, U. Weimar, M. Schweizer-Berberich, W.

Göpel, Solid State Phenomena,51-52, (1996), p 441-448

41. S.S. Park and J.D. Mackenzie:Thin Solid Films 274 (1996), p.154.

42. M.I. Ivanovskaya et al:Thin Solid Films 296 (1997), p.41.

43 S.G. Ansari et al :Thin Solid Films 295 (1997), p. 271.

44 F.Gu, S.F.Wang, C.F.Song, M.K. Lu, Y.X. Qi, G.J. Zhou, D.Xu and D.R.Yuan : Chem. Phys.

Lett. 372 (2003), p.451

45 K.C. Song and J.H. Kim: J. Colloid Interface Sci. 212 (1999), p.193

46. A. Dieguez et al: Sens. Actuators B 60 (1999), p.125

47. T.Wang, Z. Ma, F. Xu and Z. Jiang: Electrochem. Comm., 5,7, (2003) p.599-602

48. F. Gu , S.F. Wang, M.K. Lu, Y.X. Qi, G.J. Zhpu, D. Xu and D.R. Yuan, J.Crystal Growth,

255,3-4, (2003), p.357.

49. H.Yang, W.Jin, L.Wang:Mat.Letters, 57,22-23, (2003) p.3686

50. E.R. Leite, , M. I.B. Bernardia, E.Longo, J.A. Varela and Carlos A. Paskocimas, Thin Solid

Films, 449, 1-2 (2004) p.67

51 S.R. Davis, A.V. Chadwick and J.D. Wright.: J. Mater. Chem. 8 9 (1998) p. 2065-2071

52. C.C. Liu, 2nd Int. Symposium .on Electrochemical Microsystem Technologies, Tokyo,

(1998), p. 32.

53. P.T. Moseley et al, Tech. and Mechanisms in Gas Sensing, Adam Hilger, Bristol, UK (1991)

62 From Nanopowders to Functional Materials

From Nanopowders to Functional Materials 10.4028/www.scientific.net/SSP.106 Review on the Production and Synthesis of Nanosized SnO2 10.4028/www.scientific.net/SSP.106.57

DOI References

[3] S. Iijima.: Nature 354 (1991), p. 56.

doi:10.1038/354056a0 [8] A.M. Morales and C.M. Lieber:Science, 279 (1998), p. 208.

doi:10.1126/science.279.5348.208 [10] M. Nagano: J. Crystal Growth 66 (1984), p.377.

doi:10.1016/0022-0248(84)90221-5 [19] Z.R. Dai, J.L. Gole, J.D. Stout, Z.L. Wang, :,J. Phys. Chem. B 106 (2002), p. 1274

doi:10.1021/jp013214r [22] S.H. Sun, G W Meng, M G Zhang, X H An, G S Wu and L D Zhang , J.Phys.D: Appl. Phys. 37 (2004)

p.409-412

doi:10.1088/0022-3727/37/3/017 [25] Y.Q.Chen, X.F. Cui, K. Zhang, D.Pan, S. Zhang, B. Wang and J. G. Hou, Chem. Physics Lett., ol.369, 1-

2, (2003) p.16-20

doi:10.1016/S0009-2614(03)00031-9 [28] S. Gupta, R. K. Roy, M.P.M. Pal Chowdhury and A. K. Pal, Vacuum, 75, 2 (2004) p.111

doi:10.1016/j.vacuum.2004.01.075 [32] C. Guo, , M. Cao and C. Hu,, Inor. Chem. Communications. 7, 7 (2004), p 929

doi:10.1016/j.inoche.2004.04.009 [34] D. S. Torkhov, A. A. Burukhin, B. R. Churagulov, M. N. Rumyantseva, and V. D. Maksimov , Inorganic

Materials, 39,11 (2003), p.1158-1162

doi:10.1023/A:1027349509269 [35] J. Zhu, Z. Lu, S. T. Aruna, D. Aurbach, and A.Gedanken,Chem. Mater, 12 (9), (2000) p. 2557

doi:10.1021/cm990683l