Thermal annealing (400°C, flow rate of 4.1 L/min using Ar/H2, 5 min) was necessary to remove residual tape adhesive and ambient molecules from the Si substrate surface. The thin graphite flakes
were imaged under an optical microscope. Single- and bilayer Opaganib molecular weight flakes were identified by examining the light intensity shift in the green channel of the red-green-blue scale relative to the contiguous substrate [8]. Photolithography was performed to form a submicron-scale Ti/Au (50:100 nm thick, respectively) semi-bowtie structure contacts with a 680-μm base separation as depicted in Figure 1a. Overall, three samples were fabricated for THz investigation: sample 2 (bilayer GR), sample 3 (single-layer GR), and sample 4 (single-layer GR grown by CVD). Based on the excellent GHz response previously reported [5], the THz
detection capabilities were subsequently investigated. The devices were mounted on a sample box designed to monitor the direct current (DC) characteristics completely insulated from the surrounding noise. The set is portrayed in Figure 1b and was modified to observe the small check details changes in the DC resistance. Figure 1 Experimental overview for THz exposure. (a) Semi-bowtie antenna structure with 680-μm gap dimension custom designed for low THz radiation. (b) THz irradiation experimental layout. (c) THz wave characteristics at the source-end side of generation. (d) THz generation setup. THz exposure pattern followed transition sequences between THz-ON/THz-OFF states for periods of 3 min as seen in Figure 2. The THz power was estimated to be 500 nW at the source-end as in Figure 1c[9]. Figure 2 THz response for sample 2 and sample 3. The blue line shows the background change which represents the transition
in the response modes for the devices, while the red line shows the actual resistance fluctuations due to the THz radiation. The change in the resistance was recorded every 30 s. Finally, the change in the sample resistance as a function of temperature was confirmed in accordance with the graphene layer thickness as shown in Figure 3. The associated characteristics of each device type, monolayer being semimetallic and bilayer being semiconducting, were used to explain the relative response to THz radiation as bolometric response. Aldehyde dehydrogenase Figure 3 Sample resistance change due to temperature variation around room temperature. The left graph shows a metallic response from samples 3 and 4 (monolayer GR device). The right graph shows a semiconductor response from sample 2 (bilayer GR device). The two devices shown as insets are implemented using the mask patterns of Figure 1a. They are identical except for the graphene thickness. Furthermore, in our recent attempt to improve the microwave transport characteristics, a new setup was used to improve the response of high-frequency operation modes. A simple two-terminal Ti/Au (50:100 nm thick, respectively) design with a gap of 10 μm was used for the GHz response experiment as seen in Figure 4a.