Optimization of Se layer thickness in Mo/CuGa/In/Se precursor for the formation of Cu(InGa)Se2 by rapid thermal annealing

• Published in: Thin solid films Vol. 535; pp. 148 - 153
• Main Authors: Koo, Jaseok, Jeon, Soyoung, Oh, Misol, Cho, Hyun-il, Son, Changgil, Kim, Woo Kyoung
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 15.05.2013; Elsevier
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Cu(InGa)Se2; Deposition by sputtering; Diffusion; interface formation; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Glass transitions; High-temperature X-ray diffraction; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Physics; Rapid thermal processing; Selenization; Solid surfaces and solid-solid interfaces; Specific phase transitions; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Rapid thermal processing; Selenization; High-temperature X-ray diffraction; Cu(InGa)Se2; Gallium; Glass; XRD; Precursor; Optimization; High vacuum; Glass transition; Cathode sputtering; Rapid thermal annealing; Size effect; Copper Indium Selenides Mixed; Physical vapor deposition; Reaction mechanism; Copper; Diffusion; X-ray diffraction analysis; Layer thickness; Molybdenum; Heat treatments; Chalcopyrite; Phase separation; Cu(InGa)Se; Bilayers
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2012.11.082

Bilayer CuGa/In precursors were deposited on low-alkali, high-strain-point glass with a thickness of 1.8mm by in-line DC-magnetron sputtering of CuGa (24Gawt%) and pure In targets. Se layers of different thicknesses, e.g., 1, 3, 5, and 8μm, were coated on the sputter-deposited glass/Mo/CuGa/In precursors with no external heating by evaporating Se in a high vacuum evaporator. Possible reaction pathways to Cu(InGa)Se2 formation from glass/Mo/CuGa/In/(Se) precursors were suggested on the basis of the high-temperature X-ray diffraction analysis. It is also proposed that the high temperature ramp rates might be preferred for the improved Ga diffusion toward the sample surface and thus reduced phase separation between CuInSe2 and Cu(InGa)Se2. In the rapid thermal process system used in this study, the Se thickness of 3μm demonstrated the best Ga incorporation during the selenization of 600nm-thick CuGa/In precursors at 550–570°C. ► Reaction pathways to Cu(InGa)Se2 from glass/Mo/CuGa/In/(Se) were suggested. ► High temperature ramp rates improved Ga diffusion during selenization of CuGa/In. ► 3μm-thick Se layer showed the best Ga incorporation during selenization of CuGa/In.