| Summary: | 碩士 === 國立交通大學 === 材料科學與工程系 === 87 === Tenary crystalline Silicon carbon nitride films have been successfully synthesized on Si wafer by MPCVD with CH4 and N2 as source gases. Some of the Si substrates were pretreated by scratching the surface with various solutions suspending with adenine, diamond paste or Si3N4 powders. The other Si substrates were deposited by adding additional Si sources without substrate pretreatments. The morphologies of the deposited films were examined by AFM and SEM. The film compositions were estimated by AES and ESCA. The bandgaps of the resultant films were investigated by CL and PL spectroscopy. The crystal structures were determined by XRD. The mechanical properties of the film were evaluated by nanoindentation technique. The field emission properties of the films were characterized by I-V measurement.
From the experimental results, the conclusions can be divided into two parts：
(A) For the conditions of adding additional Si sources and without substrate pretreatments, the deposited films possess good uniformity in morphology and compositions, and consist of 3~10 mm rectangle-shaped crystals attached with smaller hexagonal-shaped crystallites. The average atomic ratio of the resultant films is [Si]:[C]:[N]=7:3:9. The bandgaps as measured by PL and CL are around 3.01 eV and 3.87 eV, which are in the spectrum of the visible light range. The results of XRD show that the crystal structures of the films may consist of a-Si3N4, b-Si3N4and tetragonal Si3N4 types structures. The nano-hardness of the films is about 55~60 GPa.
(B) For the conditions of adding no additional Si sources but subjecting to various substrate pretreatments, the substrates pretreated by scratching with Si3N4 solution (or called "P3") show a higher nucleation density. The pity about the rest of the results is that the reproducibility of the films is very poor under various pretreatment processes and deposition conditions. The bandgaps and crystal structures of the resultant films are similar to that in part (A), except no PL signals and poorer matching of XRD patterns with a-Si3N4, b- Si3N4and tetragonal Si3N4 types structures. As to field emission properties of the films, the results show that a field emission current density can go up to 3.3 mA/cm2, under a field intensity of 22 V/mm which is much better than that for diamond films and is compatible with that for diamond-like-carbon films.
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