Strength, stiffness, and microstructure of Cu(In,Ga)Se{sub 2} thin films deposited via sputtering and co-evaporation

Journal Article · Mon Jul 07 00:00:00 EDT 2014 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4890086· OSTI ID:22303942

Luo, Shi; Jang, Dongchan; Lee, Jiun-Haw ^[1]; Liu, Chee-Wee ^[2]; Shieh, Jia-Min; Shen, Chang-Hong; Wu, Tsung-Ta ^[3]

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1. Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, No. 1, Sec 4 Roosevelt, Taipei 10617, Taiwan (China)
2. Department of Electrical Engineering, National Taiwan University, No 1, Sec 4 Roosevelt, Taipei 10617, Taiwan (China)
3. National Nano Device Laboratories, Hsinchu Science Park, No. 26, Prosperity Road I, Hsinchu 30078, Taiwan (China)

This work examines Cu(In,Ga)Se{sub 2} thin films fabricated by (1) selenization of pre-sputtered Cu-In-Ga and (2) co-evaporation of each constituent. The efficiency disparity between films deposited via these two methods is linked to differences in morphology and microstructure. Atomic force microscopy and scanning electron microscopy show that selenized films have rougher surfaces and poor adhesion to molybdenum back contact. Transmission electron microscopy and electron energy loss spectroscopy revealed multiple voids near the Mo layer in selenized films and a depletion of Na and Se around the voids. Residual stresses in co-evaporated films were found to be ∼1.23 GPa using wafer curvature measurements. Uniaxial compression experiments on 500 nm-diameter nanopillars carved out from co-evaporated films revealed the elastic modulus of 70.4 ± 6.5 GPa. Hertzian contact model applied to nanoindentation data on selenized films revealed the indentation modulus of 68.9 ± 12.4 GPa, which is in agreement with previous reports. This equivalence of the elastic moduli suggests that microstructural differences manifest themselves after the yield point. Typical plastic behavior with two distinct failure modes is observed in the extracted stress-strain results, with the yield strength of 640.9 ± 13.7 MPa for pillars that failed by shearing and 1100.8 ± 77.8 MPa for pillars that failed by shattering.

• OSTI ID: 22303942
• Journal Information: Applied Physics Letters, Vol. 105, Issue 1; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ATOMIC FORCE MICROSCOPY
COPPER SELENIDES
ENERGY-LOSS SPECTROSCOPY
EVAPORATION
FLEXIBILITY
GALLIUM COMPOUNDS
INDIUM COMPOUNDS
LAYERS
MICROSTRUCTURE
PRESSURE RANGE GIGA PA
RESIDUAL STRESSES
SCANNING ELECTRON MICROSCOPY
SPUTTERING
STRAINS
SURFACES
THIN FILMS
TRANSMISSION ELECTRON MICROSCOPY
YIELD STRENGTH