High-rate, low-temperature synthesis of composition controlled hydrogenated amorphous silicon carbide films in low-frequency inductively coupled plasmas

Abstract

It is commonly believed that in order to synthesize high-quality hydrogenated amorphous silicon carbide (a-Si1−xCx : H) films at competitive deposition rates it is necessary to operate plasma discharges at high power regimes and with heavy hydrogen dilution. Here we report on the fabrication of hydrogenated amorphous silicon carbide films with different carbon contents x (ranging from 0.09 to 0.71) at high deposition rates using inductively coupled plasma (ICP) chemical vapour deposition with no hydrogen dilution and at relatively low power densities (∼0.025 W cm−3) as compared with existing reports. The film growth rate Rd peaks at x = 0.09 and x = 0.71, and equals 18 nm min−1 and 17 nm min−1, respectively, which is higher than other existing reports on the fabrication of a-Si1−xCx : H films. The extra carbon atoms for carbon-rich a-Si1−xCx : H samples are incorporated via diamond-like sp3 C–C bonding as deduced by Fourier transform infrared absorption and Raman spectroscopy analyses. The specimens feature a large optical band gap, with the maximum of 3.74 eV obtained at x = 0.71. All the a-Si1−xCx : H samples exhibit low-temperature (77 K) photoluminescence (PL), whereas only the carbon-rich a-Si1−xCx : H samples (x ≥ 0.55) exhibit room-temperature (300 K) PL. Such behaviour is explained by the static disorder model. High film quality in our work can be attributed to the high efficiency of the custom-designed ICP reactor to create reactive radical species required for the film growth. This technique can be used for a broader range of material systems where precise compositional control is required.

Single-step, rapid low-temperature synthesis of Si quantum dots embedded in an amorphous SiC matrix in high-density reactive plasmas

“…At a glimpse, one can also notice that, with the increase of the carbon content X C , the intensity of the Si-H wagging or rocking band gradually diminishes while the intensities of the Si-H and Si-C stretching bands reveal the opposite trend. This observation agrees well with our previous work on the growth of hydrogenated amorphous silicon carbide films [24]. In this previous work, it was clearly demonstrated that the magnitude of the Si-H wagging or rocking absorption peak gradually decreased and eventually disappeared completely at an intermediate carbon content X C of 50at.% while the magnitudes of the Si-H and Si-C stretching absorption peaks had a maximum value at an intermediate carbon content X C of 50at.% [24].…”

“…The appearance of these strong interference fringes suggests that the surface of the deposited films is quite smooth. However, the absorption peaks attributed to the characteristic Si-H wagging or rocking mode located at $640 cm À1 , the stretching mode of Si-C bonds located at $780 cm À1 , and the Si-H stretching mode located at $2100 cm À1 , respectively, can still be distinctly detected in the spectra [24,28]. At a glimpse, one can also notice that, with the increase of the carbon content X C , the intensity of the Si-H wagging or rocking band gradually diminishes while the intensities of the Si-H and Si-C stretching bands reveal the opposite trend.…”

“…This shift has been attributed to the formation of grain boundaries or clustered silicon hydrides at inner surfaces of microvoids [19,29]. It has also been shown that the peak position of the Si-H stretching mode shifts from $2000 cm À1 for the amorphous Si films towards a higher wave number with the increased carbon incorporation into the film and reaches $2100 cm À1 at an intermediate carbon content of 50at.% [24]. This shift has been attributed to an increased electronegativity of silicon atoms upon greater C incorporation into the film [24,30].…”

“…These spectra have been carefully processed with VG software to fit the Gaussian peak components mixed with Lorentzian shapes using a least-squares routine, after Shirley background subtraction. The result of peak fitting performed on Si 2p spectrum yields two peaks, located at binding energies of 99.3 eV and 100.4 eV, which are ascribed to predominant Si-Si/Si-H and minor Si-C bonds, respectively [23,24]. Likewise, two peaks in the C 1s spectrum obtained from the deconvoluted spectrum are located at binding energies of 283.2 eV and 284.4 eV, which are attributed to predominant C-Si and minor C-C/C-H bonds, respectively [23,24].…”

Plasmas meet plasmonics

“…Gaseous plasmas represent an ideal fabrication environment for this purpose. A high degree of compositional control during nanoassembly has been demonstrated for plasma-based processes both computationally [113,116,134,135] and experimentally [136][137][138][139][140][141].…”