Akademik Veri Yönetim Sistemi
METALLURGICAL AND MATERIALS TRANSACTIONS B-PROCESS METALLURGY AND MATERIALS PROCESSING SCIENCE, cilt.55, sa.1, ss.589-599, 2024 (SCI-Expanded, Scopus)
Methanol is a renewable, low-carbon chemical that can be obtained from biomass. GeO2 is the main source for producing Ge, which is an important semiconductor. The current study aimed to investigate the reduction of GeO2 and chemical vapor deposition of Ge using gaseous species generated by methanol pyrolysis. Mass measurement, X-ray diffraction and scanning electron microscopy techniques were used to determine the extent of the oxide reduction, and to characterize the products. CO and H-2 were predicted as the major reducing agents derived from the methanol pyrolysis at 1000 K to 1200 K, in agreement with the experimental measurement. It was found that the mass loss in GeO2 increased to 85.5 pct as the reaction time and temperature were raised to 10 minutes and to 1200 K. The GeO2 reduction was insignificant at 900 K, in contrast to the thermodynamic prediction, essentially owing to the sluggish reaction kinetics. At 1000 K, the significant reduction of GeO2 to Ge, close to the thermodynamic equilibrium, was attained. At 1100 K to 1200 K, the experimental mass loss was more than the thermodynamics prediction. The discrepancy was explained by a mass-transport theory involving boundary layer in the gas phase over the powder bed. Ge films were deposited from the gaseous species generated upstream at 1200 K for 10 minutes on a Si (400) substrate held downstream in the reaction tube at 723 K to 923 K. Polycrystalline rough Ge thin films with pillar-like crystals were obtained when the substrate temperatures were 723 K and 823 K. At 923 K, a denser polycrystalline Ge film was grown probably owing to the enhanced Ge diffusion on the substrate surface.