本論文的主題分為四部分: (1)以SiH4、C2H2和H2為反應物的低壓化學氣相沉積系統探討Si(111)上碳化緩衝層表面的石墨化及其對成長3C-SiC(111)磊晶膜的影響之研究; (2)以SiH4、C2H2和H2為反應物的低壓化學氣相沉積系統在Si(100)上表面碳化改質及其對成長3C-SiC(100)磊晶膜的影響之研究; (3)以超高真空化學氣相沉積系統來研究GeH4在Si(100)表面分解後形成Ge沉積的反應動力機制，並且配合量子化學計算來推論反應機制; (4)以超高真空電漿輔助化學氣相沉積系統在c-Si基材上成長a-Si:H本質鈍化層於太陽能電池應用之研究。
第一部分的實驗中，我們以C2H2和H2為反應物的低壓化學氣相沉積系統在Si(111)上進行表面碳化改質成為SiC，並於改質後的表面通入SiH4和C2H2進行3C-SiC(111)的磊晶膜成長。實驗結果發現，於單晶矽上碳化矽異質磊晶程序中，碳化處理後的矽表面理當呈現完整的SiC緩衝層會因為短時間的退火而造成緩衝層石墨化。由於石墨化的緩衝層具有較低的表面能，之後3C-SiC(111)薄膜成長在石墨化SiC緩衝層表面的成長因而呈現三維的成長模式。若在成長SiC薄膜之前，快速將碳化後的晶片降到接近室溫再由低溫直接通入SiH4和C2H2再升溫到長膜溫度時，則可以防止這種表面石墨化的發生;且二維成長的SiC(111)膜可以發生在此碳化後的緩衝層上，並且具有較高結晶品質。
在第二部分的研究中，我們以同樣的碳源氣體進行Si(100)晶面上的碳化表面改質，並嘗試成長3C-SiC(100)磊晶膜。實驗結果發現，對於Si(111)表面以5 × 10-2 Torr 的乙炔於1343 K 經8 min碳化處理後的表面已轉變為SiC，在Si(100)表面以相同碳化條件處理後卻呈現有過量的碳，這表示C2H2在Si(100)表面有較高的反應性。當降低乙炔分壓到1.8 × 10-3 Torr 和碳化處理時間至10 sec時，可以在碳化的Si(100)表面有最少的過量碳(少於33%)。之後，較好的SiC(100)薄膜可以成功地成長在經10 sec處理後的Si(100)表面上。
在第三部分的研究中，我們在超高真空化學氣相沉積系統中研究GeH4在Si(100) 2 × 1表面分解之反應機制，經由初期成長的動力探討發現在0.2-原子層(ML) Ge覆蓋率下的反應活化能為30.7 kcal/mol; 當Ge沉積至1 ML時，反應活化能降低至19 kcal/mol。輔以量子化學的反應模擬計算，我們認為在H原子遷移後的Si dimer鍵的打開是GeH4在Si(100)-2 × 1表面初期沉積Ge潤濕層的速率決定步驟。此外，二個及更進一步的三個dimer之計算叢集模式皆有提供額外dimer單元讓GeH3(a)上的H原子遷移到這些dimer上的活性位置，經由這個程序可以幫助克服Si dimer鍵的開環能障。鍺原子在閉環後，將會變成融入到晶格的位置裡。
最後，我們探討使用超高真空電漿輔助化學氣相沉積系統於FZ之n型Si(001)晶片上成長各種本質a-Si:H鈍化層的載子有效生命週期，即使在基材溫度於100oC及低[H2]/[SiH4]稀釋比(10)下，成長出5 nm的本質a-Si:H薄層在單晶基材上仍呈現明顯的結晶化現象，結晶化的鈍化層具有與矽晶基材相同的能隙，造成鈍化後的矽晶載子有效生命週期較低。另外，在反應時填加CO2氣體以形成含氧約10 %的a-SiOx:H，可以有效地預防鈍化層結晶化。經由 µ-PCD量測的結果，具有較寬能隙的鈍化材料a-SiCxOyNz:H薄層，可增加矽晶的載子有效生命週期至2255 µs，且表面覆合速率低至5.5 cm/s，具有良好的鈍化效果。

The subject of this research is focused on: (1) effect of surface graphitization of the SiC buffer layer on the growth mode and crystallinity 3C-SiC(111) films formed through chemical vapor deposition(CVD); (2) surface carbonization of Si(100) by C2H2 and its effects on the subsequent SiC(100) epitaxial film growth; (3) mechanism of growth of the Ge wetting Layer upon exposure of Si(100)-2 × 1 to GeH4; (4) effect of crystallization of a-Si:H passivation layers on surface recombination velocity for n-type Si solar cells.
In the first part, we have grown 3C-SiC(111) films epitaxially on Si(111) through low pressure CVD using SiH4, C2H2, and H2 as reactant gases. We used X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy to investigate the effects of the surface graphitization of the carbonized Si(111) on the mode and crystallinity of the subsequent SiC film growth. A disordered crystalline graphite layer was formed after annealing the as-carbonized Si(111) substrate under a H2 ambient at 1343 K for 5 min. The 3C-SiC(111) film grew on the graphitized buffer layer via a three-dimensional growth; this growth was two-dimensional on the surface that had not been subjected to annealing. This behavior correlated with the different in surface energies of the two types of buffer layer.
In the second part, surface carbonization of Si(100) using C2H2 as the carbon source was performed in a cold-wall-type CVD reactor at a low pressure of 5 Torr. The carbonization process as a function of C2H2 partial pressure and treatment time was investigated using XPS. It was found that in comparison with a complete transformation to SiC surface on Si(111) by 8 min treatment of 5×10-2 Torr C2H2 at 1343 K, the carbonization on Si(100) under the same condition forms excessive carbon, plausibly due to the larger C2H2 adsorption heat on Si(100) surface. Reducing C2H2 partial pressure to 1.8×10-3 Torr and treatment time to 2 min was enough for Si(100) to form a saturated carbide layer of about 2.0 nm in thickness. Subsequent 3C–SiC(100) epitaxial film growth was found successful especially on a 10 s carbonization- treated surface that has the least amount of excessive carbon.
In the third part, we report the initial reaction kinetics for Ge deposition after exposing a Si(100)-2 × 1 surface to GeH4 in a ultra high vacuum chemical vapor deposition system. The growth rate of Ge, especially at the wetting layer stage, was investigated using in situ XPS to measure the signals for Ge atoms at the onset of deposition. A kinetic study concerning the growth of the wetting layer revealed an activation energy of 30.7 kcal/mol for a ca. 0.2-monolayer Ge coverage. This governing energy barrier correlates well with the results of density functional theory calculations, which suggested that opening of the Si dimer following a H atom migration would be the rate-controlling step for the initial growth of the Ge wetting layer on Si(100)-2 × 1 from GeH4. In addition, two- and three-dimer cluster models provided us with extra dimer units with which to model the H atom migration from GeH3(a) to an open site; this process assists the system to overcome the energy barrier for the opening of the Si dimer bond. The Ge atom then became incorporated into the lattice after ring closure.
In the final part, surface passivations for the amorphous/c-Si heterojunction structure of solar cells were performed by plasma enhanced chemical vapor deposition reactor. The correlation of effective carrier lifetime and surface crystallization of the various passivation layers were investigated by microwave photoconductivity decay (µ-PCD) and RHEED. It is found that a-Si:H layer of 5 nm in thickness grown on c-Si showed a crystalline structure even at a low [H2]/[SiH4] dilution ration of 10 and a low substrate temperature of 373 K. Adding oxide of 10 at. % to form a a-SiOx:H was effective in preventing the passivation layer from crystallization. µ-PCD measurements showed that Si wafers with wide bandgap a-SiCxOyNz:H exhibited a high effective carrier lifetime up to 2255 µs. The surface recombination velocity of a-SiCxOyNz:H passivated wafer was calculated as low as 5.5 cm/s, indicating a good surface passivation effect.

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