Fully Transparent p‐MoTe₂ 2D Transistors Using Ultrathin MoO_x/Pt Contact Media for Indium‐Tin‐Oxide Source/Drain

Abstract

Since transition metal dichalcogenide (TMD) semiconductors are found as 2D van der Waals materials with a discrete energy bandgap, many 2D-like thin field effect transistors (FETs) and PN diodes are reported as prototype electrical and optoelectronic devices. As a potential application of display electronics, transparent 2D FET devices are also reported recently. Such transparent 2D FETs are very few in report, yet no p-type channel 2D-like FETs are seen. Here, 2D-like thin transparent p-channel MoTe 2 FETs with oxygen (O 2 ) plasma-induced MoO x /Pt/indium-tin-oxide (ITO) contact are reported for the first time. For source/drain contact, 60 s short O 2 plasma and ultrathin Pt-deposition processes on MoTe 2 surface are sequentially introduced before ITO thin film deposition and patterning. As a result, almost transparent 2D FETs are obtained with a decent mobility of ≈5 cm 2 V −1 s −1 , a high ON/OFF current ratio of ≈10 5 , and 70% transmittance. In particular, for normal MoTe 2 FETs without ITO, O 2 plasma process greatly improves the hole injection efficiency and device mobility (≈60 cm 2 V −1 s −1 ), introducing ultrathin MoO x between Pt source/drain and MoTe 2 . As a final device application, a photovoltaic current modulator, where the transparent FET stably operates as gated by photovoltaic effects, is integrated.

Monolithic Interface Contact Engineering to Boost Optoelectronic Performances of 2D Semiconductor Photovoltaic Heterojunctions

“…The transition metal oxide interlayer, inserted between the electrode and the active layer, has been widely used for this purpose in organic and quantum dot solar cells. − This n -type oxide layer injects electrons into the valence band of the active layer, effectively extracting positively charged holes. − However, the approach using such an interlayer to improve the photovoltaic performances in 2D TMD heterojunctions has not yet been demonstrated. In addition, the previous reports used the vacuum deposition and O 2 plasma processes to insert the oxide layer, which can damage the active layer and cause performance degradation. − In this study, we propose the monolithic fabrication of tungsten oxide (WO x ) for use as a hole extraction layer in the WSe 2 –MoS 2 p – n heterojunctions. The formation of a WO x /WSe 2 junction by the monolithic oxidation induces the effective tuning of the Fermi level ( E F ) of WSe 2 and promotes hole extraction through favorable band alignments at the heterointerface.…”

Complementary Type Ferroelectric Memory Transistor Circuits with P‐ and N‐Channel MoTe2

“…Possible contact improvement methods such as O 2 plasma treatment of p-MoTe 2 surface before Pt contact could be conducted for future work to improve the memory cell performances. [46] For main primary application of our complementary type cell (inset circuits), nonvolatile FeNVM www.advelectronicmat.de of 100 mV is applied, output voltage signals were measured to be 80 mV and 0 V for PROGRAM and ERASE by ±20 V 1 s pulses, respectively as shown in Figure 4d. Those two output voltage states were maintained for more than 500 s according to another retention measurement.…”

Nonvolatile and Neuromorphic Memory Devices Using Interfacial Traps in Two-Dimensional WSe2/MoTe2 Stack Channel

“…Although we could not resolve the trap DOS at the heterojunction interface even in HRSTEM images, the trap DOS can be analytically depicted with each device condition and its corresponding band diagrams as respectively shown in Figure a–c and d–f. , Parts b and e of Figure show the initial pristine case of our stacked channel FET without gate pulse. The band diagram in Figure e describes the source and drain contacting WSe 2 , which interfaces with MoTe 2 .…”