Capacitance voltage curves

Fig. 13. (a) High frequency (1MHz) capacitance-voltage curves for Al/octadecyl/... 

Si(lll) structures formed on n- and p-doped substrates showing the typical accumulation (acc), depletion (dep) and inversion (inv) regimes, (b) Capacitance-voltage curves (1MHz) in the dark (circles) and under white illumination (squares) for a structure formed on a p-doped substrate. The increase in capacitance under illumination in positive bias is characteristic of the formation of an inversion layer. Reprinted from [25]. 

Figure 16.4 Dynamic capacitance-voltage curves of an organic MIS capacitor measured at 1 Hz for different gate-bulk voltage (V(3b) sweep directions at different temperatures. The organic semiconductor is a 48 nm thick poly(3-octylthiophene)...

Su et al. have recently employed QELS to study the potential-induced assembly of Au nanoparticles at the water/DCE interface [31]. The water-soluble Au nanoparticles featured an average diameter of 1.5 0.4 nm and were capped by mercaptosuccinic acid (MSA). The capacitance-voltage curves in Fig. 4.12a show an increase in the differential capacitance (Qi) at negative with increasing concentration of the nanoparticles in the aqueous phase. As illustrated in... 

Figure 27.17. Capacitance-voltage curves of CC SiC-600C at the potential sweep rate of lOmV/s (1) IL (2) 50% H2SO4 (3) 30% KOH.

Figure 27.18. Capacitance-voltage curves for CCs in 50% H2SO4 at 20 mV/s (1) TiC-600C (2) SiC-600C (3) TiC-lOOOC (4) SiC-1500C.

A similar situation exists in an insulated gate structure the difference between the WF of the semiconductor and the gate metal adjacent to the insulator causes a deficiency or an excess of electrons in the semiconductor at its interface with the insulator. In the semiconductor/insulator/metal diodes the amount of the excess charge at the semiconductor plate is determined from the capacitance-voltage curves while in a field-effect transistor the excess charge at the semiconductor/insulator interface is related to the magnitude of the drain-to-source current [13]. In either case the observed WF difference contains the contribution from both the bulk and from the surface (or interface). 

If there is a pretilt, i.e., the director tilt angle at the walls is nonzero, the changes near Vq are gradual. We then define as the intersection of the extrapolated linear portion of the capacitance/voltage curve with the horizontal C=C(V 0) curve (see Fig. 1). We assume the surface coupling to be strong, so that the tilt angle at the surface is constant. 

A small pretilt at the walls is usually introduced in order to suppress areas of reverse tilt and twist. The value of used in the calculation was obtained from the capacitance/voltage curves. The pretilt appears to lower Nj ax (see Fig. 4) and should therefore be kept to a minimum d=10 ym, X= 0.6353 ym, no=1.549, ne 1.764. 

In addition, results by Armstrong and Mason (23) show similar shapes of capacitance-voltage curves for RbAg I Pt at 22° and 95°C and for Agl Pt at 200°. It seemed worthwhile, then, to attempt to develop a simple theoretical "adsorption capacitance" model and compare it with available data. 

To compare the theory with experimental results, we see if the capacitance expression of Eq. 14 can be fitted to the central region of Fig. 4 with a reasonable value of AzJ. In Fig. 10, the 417 experimental AgBr Pt capacitance-voltage curve of Fig. 4 is replotted on a linear scale. On the same graph, the theoretical C(e) curve is plotted, with Az chosen such that the capacitance at e = 0 equals the experimental capacitance at the midpoint... 

Fig. 10 Comparison of experimental (Fig. 4) and theoretical (Eq. 14) capacitance-voltage curves for AgBrjPt interface at 417 C. Solid curve is experimental solid with dots is theoretical. Dashed curves are theory-experiment difference curves. Az in Eq. 14 was chosen to match experimental capacitance at maximum ...

Fig. 12 Capacitance - voltage curves for p-Si in acetonitrile as a function of frequency and light intensity showing behavior expected for MOS devices in inversion.

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