Host: The Japan Society of Vacuum and Surface Science
Name : Annual Meeting of the Japan Society of Vacuum and Surface Science 2024
Location : [in Japanese]
Date : October 20, 2024 - October 24, 2024
Two-dimensional (2D) materials have attracted attention as future nanodevice materials because they are structurally stable despite their atomic-scale thickness and exhibit unique electrical and optical properties [1]. GaSe is known to be a highly photo and electrically responsive 2D material. Considering that a transistor is controlled by the gate voltage, which turns the current between source and drain on and off, the response of GaSe nanoribbons to electron irradiation is an interesting phenomenon because it can work as a switch (on and off). The response of WS2 nanoribbon suspended between electrodes against electron irradiation has been reported [2], but the results are different from those expected due probably to contaminations, and the intrinsic response has not been confirmed, yet.
In this study, we aim to investigate the intrinsic electrically response of suspended GaSe nanoribbon to irradiating electrons by our uniquely developed in-situ transmission electron microscopy (TEM) sample holder [3,4].
A special device on a silicon chip was fabricated for TEM: it has a window for TEM observation, a gold electrode of about 10 μm width crosses over a silicon nitride film covering the window, and a nanogap of about 100-200 nm is formed by cutting the electrode using focused ion beam. Thin GaSe nanoribbons were suspended over the nanogap according to the following dry transfer process. Thin and small GaSe flake, obtained by mechanical exfoliation of bulk crystal, was picked up with a viscoelastic resin, PDMS, and transferred to the nanogap by stamping (Fig. 1(a)). Figure 1(b) shows a TEM image of the GaSe nanoribbon.
The current passing through the GaSe nanoribbon was measured by applying a bias voltage of 2 V between the nanogap. The cycle of irradiating electrons for 10 seconds and stopping for 60 seconds was repeated. As shown in Figure 1(c), the current varied sharply with this cycle, showing the electrically response of suspended GaSe nanoribbon clearly. The current density was 7600 A/m2 during electron irradiation, while it was only 30 A/m2 during non-irradiation.
References:[1] K. S. Novoselov, et al., Nature 438, 197–200 (2005). [2] Y. Fan, et al., ACS Appl. Mater. Interfaces 8, 32963 (2016). [3] C. Liu, et al., Carbon 165, 476-483 (2020). [4] C. Liu, et al., Nanotechnology 32, 025710 (2020).
