In both instances, the band gap can be ideally tuned in order to match the low-energy photons in the gigahertz (GHz)/terahertz (THz) regime. This is in marked contrast to conventional semiconductors whose band gaps appear several KU55933 orders of magnitude larger. For these reasons, graphene field-effect transistors (GR-FETs) have the potential to exceed the detection limit of most existing semiconductor quantum point contacts [3, 4]. This is due to the unique phase-coherent length of open quantum dot structures that can be formed in bilayer graphene when exposed to GHz/THz radiation [5]. An additional benefit of the GR-FET platform in relation to structures based
on carbon nanotubes includes the high level selleck chemical of similarity with conventional integrated semiconductor FET fabrication techniques. Considering the mentioned benefits, GR-FETs are emerging as excellent candidates for developing a broadly tunable GHz/THz sensor. In particular, the realization of THz detection will be important for future developments in medical imaging, spectroscopy, and communication, which all exploit the unique linear nonionizing benefits of THz radiation [6]. Existing GR-FETs have been fabricated by micromechanical exfoliation of highly oriented pyrolytic graphite
(HOPG-SG2) contacted with two-terminal submicron-scale metal electrodes (Ti/Au or Pd/Au) [5]. The microwave transconductance characteristics show excellent photoresponse Histamine H2 receptor GSI-IX manufacturer around the X band (approximately 10 GHz) but quickly cut off thereafter. The observed cutoff frequency was determined to be a result of the measurement wiring rather than the intrinsic response of the graphene. The positive results of this study indicate that THz detection is possible and that many of the same
experimental components could remain constant for THz irradiation experiments. Hence, this study presents the results of such THz irradiation experiment, where the same sample box design used in the previous GHz response measurement was used to test the THz detection capabilities of several GR-FETs. The results of this study and of the former GHz response study revealed numerous complementary areas for improvement. Therefore, this work also investigates experimental improvements to the wiring setup, insulation architecture, graphite source, and bolometric heating detection of the GR-FET sensor in order to extend microwave photoresponse past previous reports of 40 GHz and to further improve THz detection. Methods The devices used in this experiment were fabricated following an established procedure [7]. Thin graphite flakes were exfoliated from natural Kish graphite using adhesive tape and then transferred onto a conducting p-type Si substrate capped with a layer of 300-nm-thick SiO2.