Acoustoelectric transport at gigahertz frequencies in coated epitaxial graphene

The strain and piezoelectric potentials accompanying surface acoustic waves (SAWs) provide a powerful tool for the manipulation of elementary excitations (carriers, spins, excitons, flux quanta, etc.) in low-dimensional structures. In the case of a two-dimensional electron gas lying close to the surface of a piezoelectric substrate, the interaction between the SAW and electric charges can induce electric currents. We have recently demonstrated these acoustically induced electric currents in epitaxial graphene on SiC [1]. The weak piezoelectricity of the SiC substrate, however, lead to acoustoelectric currents of only a few pA.

Fig. 1(a) Experimental setup. The structured graphene on SiC is coated with a dielectric HSQ/SiO₂ and a piezoelectric ZnO layer before deposition of interdigital transducers for SAW excitation (IDT₁) and detection (IDT₂). (b) Dependence of the acoustoelectric current measured in graphene, I_ae, on the frequency and power of the RF signal applied to IDT₁ to generate SAWs.

In this contribution, we study structures for the efficient generation of SAWs in epitaxial graphene with frequencies compatible with those of radio-frequency (RF) electronic devices (>> 1 GHz). For that purpose, we coated our graphene Hall bar structures with a hydrogen-silsesquioxane (HSQ) layer and a piezoelectric ZnO/SiO₂ layers stack, cf. Fig. 1(a). Finally, acoustic delay lines with interdigital transducers (IDTs) were deposited at the opposite edges of the graphene Hall bars for the excitation and detection of SAWs. We have measured the acoustoelectric current, I_ae, along the graphene structures for the different acoustic modes generated by the IDTs. Figure 1(b) shows the dependence of I_ae on the frequency and nominal power of the RF signal applied to the IDT for the case of a SAW of 1.99 GHz frequency. The observed current levels are about 300 times larger than the ones previously obtained in samples with uncoated graphene Hall bars [1]. We attribute this large current enhancement to the stronger piezoelectric fields induced by the piezoelectric ZnO layer in the graphene with respect to the ones originated only by the weak piezoelectric SiC substrate.

2	Autor	A. Hernández-Mínguez , A. Tahraoui , J. M. J. Lopes , P. V. Santos
	Titel	Acoustoelectric transport at gigahertz frequencies in coated epitaxial graphene
	Source	Appl. Phys. Lett. , 108 , 193502 ( 2016 )
DOI : 10.1063/1.4949756 \| Download: PDF \| 2779 Cite : Bibtex RIS @article{ author = { A. Hernández-Mínguez and A. Tahraoui and J. M. J. Lopes and P. V. Santos }, title = { Acoustoelectric transport at gigahertz frequencies in coated epitaxial graphene }, journal = { Applied Physics Letters }, volume = { 108 }, year = { 2016 }, pages = { 193502 } } A. Hernández-Mínguez, A. Tahraoui, J. M. J. Lopes, and P. V. Santos TY - JOUR AU - A. Hernández-Mínguez AU - A. Tahraoui AU - J. M. J. Lopes AU - P. V. Santos TI - Acoustoelectric transport at gigahertz frequencies in coated epitaxial graphene JF - Applied Physics Letters JA - Appl. Phys. Lett. J1 - APL VL - 108 SP - 193502 PY - 2016/05/13

1	Autor	P. V. Santos , T. Schumann , M. H. Oliveira Jr. , J. M. J. Lopes , H. Riechert
	Titel	Acousto-electric transport in epitaxial monolayer graphene on SiC
	Source	Appl. Phys. Lett. , 102 , 221907 ( 2013 )
Download: PDF \| 2405 Cite : Bibtex RIS @article{ author = { P. V. Santos and T. Schumann and M. H. Oliveira Jr. and J. M. J. Lopes and H. Riechert }, title = { Acousto-electric transport in epitaxial monolayer graphene on SiC }, journal = { Applied Physics Letters }, volume = { 102 }, year = { 2013 }, pages = { 221907 } } P. V. Santos, T. Schumann, M. H. Oliveira Jr., J. M. J. Lopes, and H. Riechert TY - JOUR AU - P. V. Santos AU - T. Schumann AU - M. H. Oliveira Jr. AU - J. M. J. Lopes AU - H. Riechert TI - Acousto-electric transport in epitaxial monolayer graphene on SiC JF - Applied Physics Letters JA - Appl. Phys. Lett. J1 - APL VL - 102 SP - 221907 PY - 2013/01/01

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Acoustoelectric transport at gigahertz frequencies in coated epitaxial graphene

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