Hetero-Epitaxial Growth of 3C-SiC on Si (111) by Plasma Assisted CVD

The effects of C3H8 on the microstructures of the films on Si (111) have been investigated by changing the concentration of C3H8 from 0.5% to 5%. 3C-SiC film on Si (111) grown at the C3H8 concentration of 1% with relatively high flow rate of SiH4 (30 sccm) is single crystal and free from the contamination of W2C. By comparing the deposition rates of the films on Si (111) and Si (100) at different concentrations of C3H8, SiC growth on Si (111) is much more dependent on C3H8 concentration than that on Si (100). From these results it is suggested that SiC growth on Si (111) is strongly influenced by hydrogen radicals generated from C3H8 decomposition by the plasma and forms single crystal easier than on Si(100). It is expected that 3C-SiC epitaxial growth on Si (111) has higher deposition rate and lower substrate temperature than on Si (100). The crystallinity has been investigated by a reflection electron diffraction (RED) and a X-ray diffraction (XRD). The thickness and the surface roughness of the films were investigated by an ellipsometric measurement.

Hetero-Epitaxial Growth of 3C-SiC on Silicon Substrates by Plasma Assisted CVD

3C-SiC films grown on carbonized Si (100) by plasma-assisted CVD have been investigated with systematic changes in flow rate of monosilane (SiH4) and propane (C3H8) as source gases. The deposition rate of the films increased monotonously and the microstructures of the films changed from 3C-SiC single crystal to 3C-SiC polycrystal with increasing flow rate of SiH4. Increasing C3H8 keeps single crystalline structure but results in contamination of α-W2C, which is a serious problem for the epitaxial growth. To obtain high quality 3C-SiC films, the effects of C3H8 on the microstructures of the films have been investigated by reducing the concentration of C3H8. Good quality 3C-SiC single crystal on Si (100) is grown at low net flow rate of C3H8 and SiH4, while 3C-SiC single crystal on Si (111) is grown at low net flow rate of C3H8 and high net flow rate of SiH4. It is expected that 3C-SiC epitaxial growth on Si (111) will take placed at a higher deposition rate and lower substrate temperature than that on Si (100).

Structural and Morphological Characterization of Nanostructured Cobalt Ferrite Thin Films by Pulsed Laser Deposition

ABSTRACTCobalt ferrite (CoFe2O4) thin films were deposited on quartz and single crystalline MgO(001) substrates using pulsed laser deposition (PLD) technique. The orientation of the as-deposited films were investigated as a function of substrate temperature (TS) in the range 200°C – 750°C. Films grown on MgO at higher substrate temperature were found to be (001) oriented while the films grown at lower substrate temperature were polycrystalline in nature. Magnetic measurements reveal that films deposited at lower substrate temperature had lower magnetic moment compared to that of films grown with higher substrate temperature, indicating the correlation between magnetic order and crystallinity. This is attributed to the presence of ordered magnetic domains in the oriented films even though the microstructure remains the same.

Suppression of Plasma Damage on SnO2 by Means of a Different Surface Chemistry Using Dichlorosilane

ABSTRACTWe report on that plasma damage on SnO2 can be suppressed by using surface termination by chlorine. It was found that the darkening of SnO2 is decreased and a wider gap p-a-Si material is obtained by using SiH2Cl2 especially at the higher reaction pressure and at the lower substrate temperature. The suppression of darkening of SnO2 and wide optical gap is correlated to chlorine contents in the film. It is demonstrated that SiH2Cl2 is also beneficial for boron-doped material, indicating a suitable material for a window layer of solar cells.

H2-Dilution vs. Buffer Layers for Increased Voc

Hydrogen dilution and buffer layers, as two ways to obtain higher Voc values in a-Si:H p-i-n solar cells, are directly compared in the present study. Special emphasis is laid on stability against light soaking. H2-dilution in combination with lower substrate temperature yields higher Voc values and better stability as compared to buffer layers. However, light absorption is decreased due to the increased gap in H2-diluted cells. The stability of buffer layer cells can remarkably be ameliorated by boron doping and H2-dilution of the a-SiC:H buffer layer. However, stabilized efficiency is higher for optimized diluted cells than for cells with a buffer layer. An a-Si/a-Si stacked cell with a graded dilution for both cells yielded 10% initial efficiency with 17% relative degradation. Diluted a-Si:H cells at lower temperature become specially interesting in combination with a microcrystalline bottom cell. For such a “micromorph” tandem cell we obtained 11.4% initial efficiency.

Low Temperature Epitaxial Growth of TiO2 Rutile Films by ICB Deposition and Mechanical Properties in Helium Implanted Rutile Films

ABSTRACTReactive ionized cluster beam (RICB) deposition has been used to form crystalline titanium dioxide films on various substrates. Epitaxial ruble films could be formed on Al (111) and sapphire (0001) and (1120) substrates at 450 ºC and 500 ºC , respectively. We also could grow highly oriented rutile films on Si and Ge wafers and Pt (111) and (100) pdycrystal films at 400 °C . The formation of rutile films at lower substrate temperature than 500 °C has not yet been reported to be realized by other techniques.The surface microhardness has been measured in epitaxial and polycrystal TiO2 rutile films unimplanted or implanted with 150keV He ions. The microhardness of the epitaxial films is much higher and it increases with rising dose stronger than in the case of polycrystalline films. At high doses, however, the microhardness decreases rapidly in epitaxial films. The mechanical properties of the epitaxial films are superior to those of polycrystalline films.