Unseeded vapor deposition of ZnTe crystals

• Main Author: Alcantara, Norberto T.
• Format: text
• Language: English
• Published: Animo Repository 2001
• Subjects: Zinc telluride crystals; Chemical vapor deposition; Vapor-plating
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/4802
• Institution: De La Salle University

ZnTe was grown by unseeded vapor deposition. In this technique, source materials of Zn (99.8% purity) and Te (99.7% purity) with approriate stoichiometric composition were poured in an ultrasonically cleaned quartz tube, evacuated, and sealed in a high vacuum at 5x10-6 Torr. The ampoules were set horizontally in a tubular furnace with the end containing the source materials heated at 850°C, while keeping the other end of the tube at 800°C for 48 hours of pre-reaction. After cooling down to room temperature, the ampoules were removed, and the reacted ZnTe ingots were retrieved and set again in the horizontal tubular furnace for the growth stage. In the growth stage, the end containing the ingot was heated at 850°C, while the other end was kept at 800°C for 36 hours. EDX results showed that the best grown crystal had an atomic composition of 48.9% Zn and 51.1% Te. The other ZnTe crystals grown had atomic compositions of 47.57% Zn and 52.43% Te, 58.38% Zn and 41.62% Te, 55.8% Zn and 44.20% Te. SEM analysis showed that the ZnTe crystal samples were polycrystalline. The crystal with composition of 48.9% Zn and 51.1% Te showed facets that are characteristic of a cubic crystal, while the other had irregular crystallographic patterns. XRD diffraction patterns of the ZnTe crystals grown, showd sharp diffraction peaks due to (111), (200), (220), (311), (400), (331), (420), (422), and (511) planes, indicated a face-centered cubic structure. The lattice parameters of the crystals were calculated and found to have values of 6.1160Å…, 6.0492Å…, 6.1070Å… and 6.0994 Å…. These values closely match the ASTM (powder diffraction standard) for ZnTe of 6.1026Å…. Extraneous peaks were also evaluated and found to be most probably due to contamination during the XRD test process, as they were not detected in the EDX analysis.