Al/Al2O3/Al single electron transistors operable up to 30 K utilizing anodization controlled miniaturization enhancement

Abstract

We have developed a method, anodization controlled miniaturization enhancement (ACME), to make ultrasmall tunnel junctions. Anodization of electron-beam fabricated Al/Al2O3/Al tunnel junctions reduces their effective areas and capacitances, which realizes single electron transistors operating at high temperatures up to nearly 30 K. The limit of the increase in the charging energy is attributed to the initial scattering in the junction sizes.

Metal point contacts and metal-oxide tunnel barriers fabricated with an AFM

“…The difference in the two values presumably arises because of variations in tip geometry which affect the local electric field. These values of −dt/dV are slightly higher than values measured for conventional anodization of Al films but are consistent with values recently reported in the literature for nonplanar geometry [12].…”

“…Nakamura et al have shown that gross anodization of an entire Al/Al 2 O 3 SET device, guided by in situ electrical measurements, can be used to shrink its dimensions and consequently raise its operating temperature [12]. The limitation in this approach is the inevitable asymmetrical size of the tunnel junctions which are fabricated by electron-beam lithography.…”

Double oxidation scheme for tunnel junction fabrication

“…With values from Fig. 4 [24][25][26][27] Our value for specific capacitance is therefore in line with previously measured values for standard Al-AlO x -Al junctions.…”

Stable neutral Fermi ball

“…In this figure the condition for The upper shadowed region is excluded by the stability condition. The other shadowed regions are excluded by the experiments MACRO [17], KEK [19], MICA [15] and CDMS [16]. We take q = 1 for simplicity (see text).…”