Collective behavior of single electron effects in a single layer Si quantum dot array at room temperature

In this paper, we report direct experimental evidence of collective single electron effects in a single layer Si quantum dot (Si-QD) array at room temperature. The unique peak structure, observed in both the $I\text{−}V$ and the capacitance-voltage $\left(C\text{−}V\right)$ characteristics, differs remarkably from the peaks and the staircase structures reported for the case of an individual quantum dot and reveals the collective Coulomb blockade and the quantum confinement effects in the weakly coupled Si-QD array. Simple theoretical estimations have been made to interpret the origin of the unique peak structure. Moreover, the number of charged electrons for each peak calculated from the underlying area of the peaks both in the $I\text{−}V$ (after subtracting the background current) and the $C\text{−}V$ characteristics is found to be consistent with the number of coupled quantum dots under the electrode. This good agreement supports the assumption that each peak in the characteristics corresponds to a collective charging process of single electron into a subband in the Si-QD array arising from the weakly interdot coupling. This collective single electron effect in Si-QD array is important for its future application in the nanoelectronic devices.

Figure 1

A plane-view AFM image of the Si-QD array after the gate $\mathrm{Si}{\mathrm{O}}_2$ layer having been removed by diluted HF solution.

Figure 2

(a) A typical $I\text{−}V$ curve with sharp-edged platformlike peaks, which are divided into two regions according to their positions in voltage. The schematic band diagram is shown in the top-left inset. (b) The accumulative injected charges as a function of the voltage ramping.

Figure 3

The details of the peak structure, (a) for the two peaks in region I and (b) for last three peaks in region II. Each peak has an abrupt current jump ($\Delta I_{\mathit{\text{jump}}}$, listed in Table ) at the “onset” and a sustaining charging current until an abrupt current drop at the “end.”

Figure 4

Frequency-dependent $C\text{−}V$ characteristics of (a) the sample (annealed) with well-defined Si-QDs measured at different ac frequencies, in which discrete capacitance peaks are observed; (b) the reference sample (unannealed) measured at different ac frequencies, in which no peaks but a shoulder are observed.