Cat-CVD-prepared oxygen-rich μc-Si:H for wide-bandgap material

Microcrystalline phase-involved oxygen-rich a-Si:H (hydrogenated amorphous silicon) films have been obtained using catalytic chemical vapor deposition (Cat-CVD) process. Pure SiH₄ (silane), H₂ (hydrogen), and O₂ (oxygen) gases were introduced in the chamber by maintaining a pressure of 0.1 Torr. A tungsten catalyzer was fixed at temperatures of 1750 and 1950 °C for film deposition on glass and crystalline silicon substrates at 200 °C. As revealed from X-ray diffraction spectra, the microcrystalline phase appears for oxygen-rich a-Si:H samples deposited at a catalyzer temperature of 1950 °C. However, this microcrystalline phase tends to disappear for further oxygen incorporation. The oxygen content in the deposited films was corroborated by FTIR analysis revealing SiOSi bonds and typical SiH bonding structures. The optical bandgap of the sample increases from 2.0 to 2.7 eV with oxygen gas flow and oxygen incorporation to the deposited films. In the present thin film deposition conditions, no strong tungsten filament degradation was observed after a number of sample preparations.