Temperature dependence of the acoustoelectric current in graphene

Abstract

The acoustoelectric current in graphene has been investigated as a function of temperature, surface acoustic wave (SAW) intensity, and frequency. At high SAW frequencies, the measured acoustoelectric current decreases with decreasing temperature, but remains positive, which corresponds to the transport of holes, over the whole temperature range studied. The current also exhibits a linear dependence on the SAW intensity, consistent with the interaction between the carriers and SAWs being described by a relatively simple classical relaxation model. At low temperatures and SAW frequencies, the measured acoustoelectric current no longer exhibits a simple linear dependence on the SAW intensity, and the direction of the acoustoelectric current is also observed to reverse under certain experimental conditions.

Controlling the properties of surface acoustic waves using graphene

“…A small change in gate bias can therefore be used to change the doping of the graphene from n-type to p-type. The resistance measured on these devices is much higher than typically obtained for CVD graphene on Si/SiO 2 substrates, probably reflecting both the effect of the lithium niobate substrate and also the relatively poor transfer of graphene onto the substrate, which results in patches of polycrystalline graphene connected only by narrow channels [27]. The field effect mobility (μ) was estimated from the field effect characteristics using μ = Δσ/(CΔVg), where σ is the sheet conductivity of graphene, and C is the gate capacitance.…”

“…For example, SAW devices that are responsive to hydrogen and carbon monoxide [19], and moisture [20][21][22][23] have been reported. Acoustic charge transport has also very recently been reported in graphene [24,25], and we have investigated it in monolayer graphene, produced by chemical vapor deposition (CVD), and transferred onto lithium niobate SAW devices, both at room temperature [26], at low temperature [27], and under illumination [28].…”

Acoustoelectric photoresponse in graphene

“…[14][15][16][17][18] Acoustic charge transport has very recently been reported in graphene, 19,20 and we have investigated it in monolayer graphene, produced by chemical vapour deposition (CVD), transferred onto lithium niobate SAW devices, both at room temperature 21 and low temperature. 22 In this paper, we show that illumination of the same devices, using blue (450 nm) and red (735 nm) light-emitting diodes (LEDs), causes an increase in the acoustoelectric current which is much larger than the associated change in the conductivity of the graphene. We believe that this is due to the piezoelectric interaction between the SAWs and the hot carrier distribution created by the illumination.…”

“…In turn, this hot carrier distribution causes a decrease in the conductivity of the graphene, 27 due to a reduction in the mobility, which manifests itself in our measurements as a change in the measured acoustoelectric current. Finally, at low temperatures, the length scale over which the SAW probes the conductivity of the graphene (approximately one half of the SAW wavelength) was found to be important, 22 reflecting, for example, the relative contribution to the conductivity of transport across the energy barriers associated with grain boundaries in the polycrystalline CVD graphene. However, in these measurements, the effect of illumination on the acoustoelectric current measured at SAW frequencies of 33 MHz and 355 MHz (corresponding to length scales of approximately 60 lm and 6 lm, respectively) is very similar, as might be expected if the conductivity of the graphene is dominated by a hot electron distribution.…”

Multilayer-graphene-based amplifier of surface acoustic waves

“…Owing to the form of the spectrum, there are many features defining the charge transport, 7,8 in particular, the high-current transport. [9][10][11] A series of related studies was performed recently to understand (i) the conductivity of graphene and its carrier dynamics, [12][13][14][15][16][17] (ii) plasmonic effects, [18][19][20][21] (iii) the own phonon generation by the carrier current, [22][23][24][25] (iv) the interaction between graphene electrons and SAWs, [26][27][28][29] and (v) sandwich-like "graphene-piezoelectric" structures, which allow one to create a new class of opto-acousto-electronic devices. [30][31][32][33][34] Nevertheless, the problem of modeling SAW amplification in graphene-based SAW amplifiers has not been studied systematically to date.…”