Methods for Characterization of Epitaxial Thin Films

- Matthew Clark -

PLT (110) Pt (110)

Analysis of thin film materials http://www.rigaku.com/en/products/xrd/ultima/app033 (accessed Nov 15, 2016).

Thin Films

• Crucial to the success of modern electronic devices

• Allows for complex layering in devices

• Many different deposition techniques: PLD, ALD, Sputtering, Spin coating etc.

Substrate (mm)

Deposited Thin Film (nm - μm)

Epitaxy

• Perfectly epitaxial thin films consist of ordered crystallite domains matching the structure of the underlying substrate

• Necessary to maximize desired properties of anisotropic materials

SubstrateFilm

Polycrystalline Film

Epitaxial Film

SubstrateFilm

Pole Figure Diagrams• X(α), φ(β) scan

• Used to determine degree of preferred orientation

• Pole figures are measured along varying crystallographic orientations

• Tailoring of preferred orientation crucial to device engineering

Polycrystalline Randomly Oriented

Polycrystalline Degree of Orientation

Crystallographic Texture http://www.doitpoms.ac.uk/tlplib/crystallographic_texture/texture_representation.php (accessed Nov 18, 2016).

Relationship Between Film and Substrate

• Heteroepitaxy

• If lattice mismatch between film and substrate is small material can conform to substrate

• Relaxation can create dislocations or defects

Res, H.; Zimmerman, M. High Resolution X-ray Diffractometry. www.bruker-webinars.com.

Reciprocal Space Mapping

• 2θ/ω , ω2θχ/φ , φ scan

• 2D representation of 3D intensity data

• Allows for characterization of lattice distortion/relaxation

• Epitaxial orientation (Mosaicity)

Konya, T. The Rigaku Journal 2009, 25 (2).

In Plane Diffraction

• 2θχ/φ , φ scan

• Reflection Intensities of thin film often weak with respect to substrate

• Diffraction from lattice planes normal to the substrate observed

• Measurement depth is controllable

Kobayashi, S. The Rigaku Journal 2010, 26 (1).

Current Work

• In situ determination of lattice strain pole figures (Kazimirov et al.)

• Employing lattice strain helps to develop modeling methodology capable of predicting alloy behavior

• In situ growth studies using synchrotron radiation (Kawamura et al.) • Diffraction experiments performed at elevated temperatures

throughout growth stage

• Synchrotron study of microstructure gradient in laser additively formed epitaxial Ni-based superalloy (Chen et al.)

• Laser additive formation, preferred orientation sometimes may deviate from the axial direction of the actual growth

References

• Li, X.; Sundaram, S.; Disseix, P.; Gac, G. L.; Bouchoule, S.; Patriarche, G.; Réveret, F.; Leymarie, J.; Gmili, Y. E.; Moudakir, T.; Genty, F.; Salvestrini, J.-P.; Dupuis, R. D.; Voss, P. L.; Ougazzaden, A. Optical Materials Express 2015, 5 (2), 380.

• Analysis of thin film materials http://www.rigaku.com/en/products/xrd/ultima/app033 (accessed Nov 15, 2016).

• Crystallographic Texture http://www.doitpoms.ac.uk/tlplib/crystallographic_texture/texture_representation.php (accessed Nov 18, 2016).

• Res, H.; Zimmerman, M. High Resolution X-ray Diffractometry. www.bruker-webinars.com.

• Kobayashi, S. The Rigaku Journal 2010, 26 (1). • Inaba, K. The Rigaku Journal 2008, 24 (1).

• Konya, T. The Rigaku Journal 2009, 25 (2).

• Mitsunaga, T. The Rigaku Journal 2009, 25 (1). • Nagao, K.;Kagami, E The Rigaku Journal 2011, 27 (2). • Xue, J.; Zhang, A.; Li, Y.; Qian, D.; Wan, J.; Qi, B.; Tamura, N.; Song, Z.;

Chen, K. Sci. Rep. Scientific Reports 2015, 5, 14903.

• Miller, M. P.; Bernier, J. V.; Park, J.-S.; Kazimirov, A. Review of Scientific Instruments 2005, 76 (11), 113903.

• Lamberti, C. Surface Science Reports 2004, 53 (1-5), 1–197.

• T. Kawamura, Y. Watanabe, S. Fujikawa, S. Bhunia, K. Uchida, J. Matsui, Y. Kagoshima, Y. Tsusaka, Real-time observation of surface morphology of indium phosphide MOVPE growth with using X-ray reflectivity technique, J. Cryst. Growth 237 (2002) 398