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Spin dependent tunneling spectroscopy in 1.2 nm dielectrics
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View: Figures


Image of FIG. 1.
FIG. 1.

curves before and after high electric field stressing.

Image of FIG. 2.
FIG. 2.

vs , where is the gate current density prestress and is the gate current density poststress minus . The peak in the curve is caused by a trap assisted tunneling current in the stressed measurement of Fig. 1.

Image of FIG. 3.
FIG. 3.

Representative SDT measurement taken with biased to correspond to the peak in the curve of Fig. 2. The measurement was taken with the magnetic field parallel to the Si/dielectric interface normal. The zero crossing .

Image of FIG. 4.
FIG. 4.

In this trace the sample is rotated in the magnetic field so that the Si/dielectric interface normal is perpendicular to the magnetic field. Note that the spectrum zero crossing g does not change, within experimental error, from the g with the interface normal parallel to the magnetic field as shown in Fig. 3.

Image of FIG. 5.
FIG. 5.

Comparison between the normalized SDT intensities as a function of (a) and the vs (b) plot of Fig. 2. The normalization of (a) is achieved by dividing the spin dependent modification to the tunneling current by the total dc current (I). The SDT response very closely follows the characteristic trap assisted tunneling peak of (b).

Image of FIG. 6.
FIG. 6.

SDT spin dependent modification to the tunneling current as a function of . Note that it peaks at about indicating the peak at in the SDT is shifted downward because direct tunneling overwhelms the trap assisted tunneling process at higher voltages.

Image of FIG. 7.
FIG. 7.

Energy band diagrams for the sample at three different values of . Note that the only plausible explanation for the tunneling current must involve electron tunneling through defects with levels corresponding to the range of the silicon band gap. The simplified sketch illustrates two dielectric defect levels, consistent with the experimental result.

Image of FIG. 8.
FIG. 8.

(a) The SDT response as a function of interface , (b) a crude schematic representation of K center DOS, and (c) a cartoon representation of the charge states of the K centers.

Image of FIG. 9.
FIG. 9.

Schematic illustration of the DOS for an array of precisely identical defects with precisely identical energy levels.

Image of FIG. 10.
FIG. 10.

(a) A more physically reasonable DOS in which each of the levels of Fig. 9 is broadened to take into account disorder. (b) The SDT response from the levels of (a). (c) Schematic illustration of the derivative of the SDT amplitude vs energy response of (b). (d) The absolute value of the derivative (c). The plot illustrated in (d) is, as discussed in the text, an approximation of the defect DOS.

Image of FIG. 11.
FIG. 11.

SDT signal intensity vs square root of microwave power. Note that the signal intensity does not saturate at the highest power level available in our measurements. This indicates that far higher sensitivities are possible.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Spin dependent tunneling spectroscopy in 1.2 nm dielectrics