Effects of microwave power on the structural and emission properties of hydrogenated amorphous silicon carbide deposited by electron cyclotron resonance chemical vapor deposition

Abstract

Hydrogenated amorphous silicon carbide (a-Si 1Ϫx C x :H) films have been deposited using an electron cyclotron resonance chemical vapor deposition system. The effects of varying the microwave power from 100 to 1000 W on the deposition rate, optical band gap, film composition, and disorder were studied using various techniques such as Rutherford backscattering spectrometry, spectrophotometry, Fourier-transform infrared absorption, and Raman scattering. Samples deposited at 100 W are found to have a carbon fraction ͑x͒ of 0.49 which is close to that of stoichiometric SiC, whereas samples deposited at higher microwave powers are carbon rich with x which are nearly independent of the microwave power. The optical gaps of the films deposited at higher microwave powers were noted to be related to the strength of the C-H n bond in the films. The photoluminescence ͑PL͒ peak emission energy and bandwidth of these films were investigated at different excitation energies (E ex ) and correlated to their optical band gaps and Urbach tail widths.Using an E ex of 3.41 eV, the PL peak energy was found to range from 2.44 to 2.79 eV, with the lowest value corresponded to an intermediate microwave power of 600 W. At increasing optical gap, the PL peak energy was found to be blueshifted, accompanied by a narrowing of the bandwidth. Similar blueshift was also observed at increasing E ex , but in this case accompanied by a broadening of the bandwidth. These results can be explained using a PL model for amorphous semiconductors based on tail-to-tail states radiative recombination. A linear relation between the full width at half maximum of the PL spectra and the Urbach energy was also observed, suggesting the broadening of the band tail states as the main factor that contributes to the shape of the PL spectra observed.

Electronic structure and hardening mechanism of Si-doped/undoped diamond-like carbon films

“…In a-C/H/Si films (Si/DLC), the I D /I G ratio is related to the size of the aromatic clusters in the films [16] and the PL effect can be interpreted with this cluster size too. The broadening of PL as we observed in our film may be attributed to the disorder broadening arising from the broadband tails [17]. The PL effect of these films can also be explained with the help of C-H n (s) and Si-H n bonding intensity as shown in Fig.…”

Visible photoluminescence from silicon-incorporated diamond like carbon films synthesized via direct current PECVD technique

“…The broadening of PL, i.e. the increase of FWHM of the PL peaks of all the samples, may be attributed to the disorder broadening arising from the broadband tails [28]. It is shown in Fig.…”

Hydrogenated amorphous silicon carbide deposition using electron cyclotron resonance chemical vapor deposition under high microwave power and strong hydrogen dilution

“…[1][2][3] In this study, we investigate a-Si 1Ϫx C x :H films grown with the electron cyclotron resonance chemical vapor deposition ͑ECR-CVD͒ technique, which has the unique characteristics of a high plasma density, high electron temperature, and controllable ion energy that can be independent of the degree of plasma ionization. 4,5 In our previous study on the effect of microwave power on ECR-CVD grown a-Si 1Ϫx C x :H, it was noted that the Si-C infrared absorption band at ϳ800 cm Ϫ1 can only be clearly seen for films deposited at high microwave powers beyond 800 W. 6 On the effect of hydrogen incorporation in a-Si 1Ϫx C x :H, previous reports have shown that stronger hydrogen dilution in the gas mixture will lead to films with lower defect densities and smaller Urbach energies, and result in improved optoelectronic properties, such as enhanced photoconductivity. 7,8 Based on these considerations, it is interesting to study a-Si 1Ϫx C x :H films with different carbon fractions ranging from xϭ0 (a-Si:H) to xϭ1 (a-C:H), deposited under a combination of high microwave power and strong hydrogen dilution.…”