Two-dimensional (2D) molybdenum disulfide (MoS₂) field-effect transistors (FETs) have been extensively studied, but most of the FETs with gate insulators have displayed negative threshold voltage values, which indicates the presence of interfacial traps both shallow and deep in energy level. Despite such interface trap issues, reports on trap densities in MoS₂ are quite limited. Here, we probed top-gate MoS₂ FETs with two- (2L), three- (3L), and four-layer (4L) MoS₂/dielectric interfaces to quantify deep-level interface trap densities by photo-excited charge collection spectroscopy (PECCS), and reported the result that deep-level trap densities over 10(12) cm(-2) may exist in the interface and bulk MoS₂ near the interface. Transfer curve hysteresis and PECCS measurements show that shallow traps and deep traps are not that different in density order from each other. We conclude that our PECCS analysis distinguishably provides valuable information on deep level interface/bulk trap densities in 2D-based FETs.

Two-dimensional heterojunction diodes with WSe 2 and MoS 2 nanoflakes respectively as p-and n-type semiconductors were fabricated on both glass and SiO 2 /p + -Si by direct imprinting. Superior electrostatic and dynamic performances were acquired from the diode on glass when an electric dipole-containing fluoropolymer was employed for encapsulation: forward and reverse current toward ideal behavior, enhanced aging/ambient stability, and improved dynamic rectification resulted. † Electronic supplementary information (ESI) available: I-V curves of another p-n diode on a SiO 2 /p + -Si substrate, parasitic capacitor induced by SiO 2 dielectric, photo-response of the unencapsulated pristine p-n diode and ambient stability of the CYTOP-capped diode. See

A 1D-2D hybrid complementary logic inverter comprising of ZnO nanowire and WSe2 nanosheet field-effect transistors (FETs) is fabricated on glass, which shows excellent static and dynamic electrical performances with a voltage gain of ≈60, sub-nanowatt power consumption, and at least 1 kHz inverting speed.

Recently, two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductors as van der Waals (vdW) materials have attracted much attention from researchers. Among many 2D TMDC materials, a few layer-thin molybdenum disulfide (MoS 2 ) and tungsten diselenide (WSe 2 ) have been most intensively studied respectively as 2D n-and p-type semiconductors. Here, we have fabricated vertical vdW heterojunction n-MoS 2 /p-WSe 2 diode with a few tens nm-thick layers by using vertically-sandwiched ohmic terminals, so that no quasi neutral region may exist between two terminals. As a result, we obtained high photo responsivity at zero volt without any electric power, and it appears comparable to those of commercially-optimized Si PN diode. Photo-voltage output of 0.3 V was easily obtained from our vdW PN diode as open circuit voltage, and can be doubled up to 0.6 V by using two PN diodes. These beneficial photovoltaic results from vdW PN diode were directly applied to PV switching dynamics and transistor photo gating, for the first time. We regard that our vdW n-MoS 2 /p-WSe 2 heterojunction diode could maximize its photovoltaic energy benefits with optimized TMDC thicknesses.

Room-temperature ferromagnetism in the large and direct bandgap diluted magnetic semiconductor zinc oxide (ZnO) is attributed to the intrinsic defects and p-orbital–p-orbital (p–p) coupling interaction.