The optical properties of amorphous Si films deposited by vacuum (∼1×$10^{-7} torr$) evaporation were investigated in the 0.5 ㎛ - 1.5 ㎛ (0.7 - 2.4 eV) spectral range. The optical constants were determined by the analysis of 2-transmittance data of a pair of samples with exactly the same physical properties except the thickness. The effects of deposition rate and hydrogenation on the optical properties were of central interest in this investigation. The calculation of optical constants is carried out by computer iteration method.
The results showed that lower deposition rate gives rise to a sample with a smaller refractive index and wider band gap, indicating more densely packed state.
Some of the amorphous Si samples were places in hydrogen atmosphere of 0.2 torr for hydrogen incorporation. Hydrogenation is achieved by diffusion of atomic hydrogen by d.c. discharge decomposition of molecular hydrogen into the sample at elevated temperatures.
The result gave hydrogenated samples to have wider gaps and smaller refractive indices as well as lower gap state density than unhydrogenated counterparts.
Samples coated with Pd thin films were found to have the same values in the width of the band gap, as hydrogenated samples, leaving the possibility of Pd film acting as a diffusion agent for atomic hydrogen to saturate dangling bonds.
It was concluded that hydrogenation and annealing of amorphous Si films at proper temperatures resulted in densely-packed, nearly ideal samples with low density of gap states with wider gap width, and smaller optical constants than as deposited samples.
진공(∼1.0 × $10^{-7} torr)$ 에서 현미경 slide glass에 증착하여 만든 비정질 Si film의 광학적 성질을 조사했다.
0.68 ∼ 2.38 ev의 photon energy 영역에서 구조는 같으나 두께가 다른 한쌍의 시료의 transmittance를 측정함으로써 비정질 Si film의 광학상수들을 구했다.
증착속도가 다른 2730Å, 2830Å 시료 한쌍과 1900Å, 2150Å 한쌍에 대한 결과는 증착속도가 느린 후자의 시료가 후자의 시료보다 측정된 파장영역에서 0.05 정도 적은 굴절율 값을 가지며, 0.04ev정도 더넓은 1.52ev의 band gap을 가지고 있다.
Hydrogenation 효과를 보기위한 두쌍의 시료 1970Å, 2180Å 쌍과 1830Å, 2050Å 쌍에서는 d.c discharge 방법으로 hydrogenation한 후자의 시료가 전자의 시료보다 0.02∼0.09 정도 작은 굴절율 값을 가지며, 0.1 eV정도 더넓은 1.6 eV의 bandgap을 보여준다. 또 Pd을 이용하여 hydrogenation한 시료도 1.6eV정도의 band gap을 나타내어, Pd을 이용한 hydrogenation 방법은 가능성을 암시하고 있다.
