Scanning gate microscopy of InAs nanowires

Abstract

Scanning gate microscopy, in which a conductive probe tip in an atomic force microscope is employed as a local, nanoscale top gate contact, has been used to characterize local carrier and current modulation effects in a 45nm diameter InAs semiconductor nanowire grown by metal organic chemical vapor deposition. Measurement of current flow in the nanowire as a function of tip position reveals that for both positive and negative tip bias voltages, carrier and current modulation is strongest when the probe tip is near the source and drain nanowire contacts, reaching a global maximum approximately 100–200nm distant from the source contact and a secondary maximum a similar distance from the drain contact and decreasing at greater tip-contact distances. This effect is explained, with verification by numerical simulation, as a consequence of the capacitance between the tip and the source and drain contacts as a function of tip location. Measurement of transconductance as a function of tip position reveals that the transconductance is approximately 80%–90% greater near the source contact than at the center of the nanowire.

A Bi2Te3@CoNiMo composite as a high performance bifunctional catalyst for hydrogen and oxygen evolution reactions

“…The additional electron accumulation in the Bi 2 Te 3 nanosheets is induced by the conductive probe tip, leading to an increase in the current ow. We attribute this effect to a combination of the increase in the effective tip-sample contact area near the edges of the nanosheets and the possibility that the TI Bi 2 Te 3 is thinner on the sides of the sheets than on top, 34 as well as to the lower surface resistivity at the edges of the nanosheets.…”

Electron transport in indium arsenide nanowires

“…Dark regions in the SGM images indicate a low current (electron depletion) and bright regions indicate a high current (electron accumulation). These regions appear to be evident near the edges of the NW where the coupling of the AFM tip (gate) to the NW channel is maximal due to the geometry of the tapered tip and the thin oxide at the edges of the NW [88]. To gain a more straight-forward understanding of these data, the transconductance measured with the AFM tip step of 6 nm in the channel is averaged over 100 nm periods, and is plotted in figure 11(b) at V DS = 0.045 V and V DS = 0.3 V. One can observe in figure 11(b) the following: (i) g 0 m is generally higher at V DS = 0.3 V than that at V DS = 0.045 V, as expected (g m = μCV DS /L 2 ); (ii) g 0 m assumes approximately the same value near the source contact (V S = 0 V) for both biases and is smaller near the drain contact for the larger V DS bias of 0.3 V, due to a stronger drain field leading to less gate modulation in that region; (iii) g 0 m is low just in the vicinity of the metal contacts, maximizes within 100 nm from either contact and then drops to the minimum toward the center of the channel.…”

Scanning gate microscopy on a graphene nanoribbon

“…The effect of the voltage-biased tip on transport through a quantum dot has been studied extensively in various material systems, e.g., GaAs, graphene and many other material systems. 9,[20][21][22][23] Localized charges have been imaged with this technique in InAs nanowires [24][25][26][27] and carbon nanotubes. 28,29 Previous experiments show concentric rings, which originate where quantum dots form either due to fabrication or localization in a disorder potential.…”