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Amorphous, glassy, organic semiconductors
Formation of $ncl$-Si in the amorphous matrix $a$-SiO$_{x}$ : H located near the anode and on the cathode, using a time-modulated DC plasma with the (SiH$_4$–Ar–O$_{2}$) gas phase ($C_{\mathrm{O}_2}$ = 21.5 мол%)
Yu. K. Undalova,
E. I. Terukovab,
I. N. Trapeznikovaa a Ioffe Institute, St. Petersburg
b Saint Petersburg Electrotechnical University "LETI"
Abstract:
The formation of
$ncl$-Si in the amorphous matrix
$a$-SiO
$_{x}$ : H using a time-modulated DC plasma at an elevated oxygen content of
$C_{\mathrm{O}_2}$ = 21.5 mol % in a gas mixture of (SiH
$_4$–Ar–O
$_{2}$) is investigated. Plasma modulation implies the repeated (
$n$ = 180) switching on (for
$t_{\operatorname{on}}$ = 5, 10, 15 s) and switching off (for
$t_{\operatorname{off}}$ = 5, 10, 15 s) of the magnet coil of the DC magnetron. The effect of self-induction is used to enhance the processes of SiH
$_{4}$ dissociation, the formation of Si nanoparticles, and the ionization of oxygen and
$ncl$-Si flows towards the electrodes. The samples are located both on an electrically isolated substrate holder near the anode and on the cathode (beyond its erosion zone). These experiments show that the shape of the dependences of the photoluminescence intensity
$I_{\operatorname{PL}}^{ncl-\mathrm{Si}}$ on the wavelength
$\Lambda$ are identical for all pairs of samples on the anode and cathode. When the
$t_{\operatorname{on}}$ value is small (
$t_{\operatorname{on}}$ = 5 s), the difference in the sample location only slightly affects the infrared (IR) spectra. At longer times ton
$t_{\operatorname{on}}$ (
$\ge$ 10 s) and a short time toff (5 s), the amorphous matrix located on the cathode is enriched with oxygen (as compared with that near the anode). The optimal plasma-modulation parameters are found to be
$t_{\operatorname{off}}/t_{\operatorname{on}}$ = 5, 10, 15/10 and
$t_{\operatorname{off}}/t_{\operatorname{on}}$ = 5, 10/15; under these conditions, the amorphous matrix has a “perfect structure” and is transparent to radiation, and the
$I_{\operatorname{PL}}^{ncl-\mathrm{Si}}$ value is the largest in the range
$\lambda\approx$ 0.75–0.9
$\mu$m.
Keywords:
modulated DC plasma, $a$-SiO$_{x}$ : H matrix, $ncl$-Si, $\{(SiH_4-Ar) + 21.5 mol\% O_{2}\}$, anode, cathode. Received: 03.07.2019
Revised: 10.07.2019
Accepted: 10.07.2019
DOI:
10.21883/FTP.2019.11.48453.9206
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