(a) Leakage currents as a function of annealing temperature for PECVD a-SiC:H and (b) Poole-Frenkel plot for data in Figure 1(a) .
EPR spin density (squares) and leakage current (diamonds) vs anneal temperature for otherwise identical a-SiC:H films described in Table I .
EPR and leakage current correlation of the 13a-SiC:H films investigated in this study. Note the three circled outlier points. These circled points correspond to sample designations in Table II : a-SiC:H5, a-SiC:H6, and a-SiC:H7.
A representative spectrum for each of the defect assignments shown in Table II .
A plot of leakage versus hydrogen content (a) and a plot of defect density versus hydrogen content (b).
This figure illustrates ln(J/E) versus E1/2 plots for 4 representative samples. A corresponds to a-SiC:H13, B corresponds to a-SiC:H9, C corresponds to a-SiC:H7, and D corresponds to a-SiC:H1 in Table II . In (i) the data are accompanied by solid lines corresponding to the slope anticipated for PF utilizing the dc dielectric constants shown in Table II . In (ii), we illustrate the same data but, in this case, compare the approximate slopes anticipated for SE. Note that the electric field E does not appear as a pre-factor in the standard SE expression. To obtain this slope, we simply divided the expression by electric field and then ignore a weak dependence in the logarithm of the reciprocal of electric field. In both plots, the data are indicated with capital letters and the calculated slope is indicated with lower case letters.
A cartoon illustration of spin-dependent variable range hopping. A magnetic resonance event (on the left) makes it possible for an electron to tunnel from one site to another whereas, if the two defect sites had spins of the same orientation, the tunneling event would be forbidden. This schematic illustrates why magnetic resonance of the defects involved in transport may be detected via measurements of (tunneling) current versus magnetic field in the presence of the appropriate frequency microwave radiation.
A comparison of conventional EPR (ΔB = 5 G) and SDT (ΔB = 10 G) spectrum for a-SiC:H13.
EDMR amplitude and leakage current vs bias voltage for the a-SiC:H film.
A plot of the spin dependent tunneling current (ΔI) divided by the total tunneling current (I). Note that this ratio is within our experimental error independent of voltage range between −2 and −1 V and +1 and +2 V. This suggests that the defect levels involved are in the mid to upper part of the SiC band gap.
Band diagrams for a Ti/5 nm a-SiC:H/Si capacitor sample at −1 V, 0 V, and +1 V. The +1 V and the −1 V biasing condition correspond to the approximate values at which measureable spin dependent tunneling EDMR can be observed. The results suggest that the defect levels involved must be in the mid to upper part of the SiC bandgap. The figures were made using the Boise state band diagram program. 74
Density, dielectric constant, composition, leakage, band gap (Eg) and defect assignments for samples utilized in Figures 4–7 .
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