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Rapid prototyping of devices using exfoliated Molybednum di-Sulphide (MoS2) and Molybdenum di-Selenide (MoSe2) requires an experimental protocol for maximizing the probability of realizing flakes with desired physical dimension and properties. In this work, we analyzed the size and thickness distribution of MoS2 and MoSe2 single crystalline flakes exfoliated using anodic bonding technique and established a correlation between physical dimension of the flakes and the bonding parameters. Anodic bonding was carried out by applying a fixed voltage of 200 V with a set temperature of 150 °C for four different bonding time intervals. On analyzing the flake parameters from the four anodic bonded substrates using the optical and atomic force microscopy, it is found that the probability of getting flakes with large lateral size (>200 μm) increases as the bonding time interval is increased. Most of these large sized flakes have thickness of more than one hundred mono-layers and a tiny fraction of them have thickness of the order of few monolayers. A similar trend was also observed for MoSe2 single crystals. To demonstrate the feasibility of this technique in rapid prototyping, ultra thin MoS2 flakes was directly bridged between two ITO electrodes and their transport properties was investigated. Micro-Raman and photoluminescence studies were taken on selected regions of the thicker and thinner exfoliated flakes and their physical properties are compared.

Brain inspired memory prototypes, such as atomristors, are touted as next generation two terminal memories for neuromorphic computation. To make rapid progress toward developing such atomic scale memory, a facile technique to fabricate atomristor prototypes has to be developed. In this work, one such simple and lithography free technique to fabricate an atomristor prototype using photoexfoliated monolayer molybdenum di-sulfide (MoS2) is illustrated. Resistive switching characteristics of the atomristor were demonstrated by applying a write voltage pulse of 10 (SET) and −5 V (RESET) for 100 s between the active tantalum di-sulfide (TaS2) and inert indium tin oxide electrodes. During the SET process (ON state), the Ta2+ ions from the active electrode diffuse through monolayer MoS2 to create a number of parallel conducting channels. The persistence of the conducting channel even after removing the SET bias drives the atomristor to the low resistance state. On applying the “RESET” bias, the device resistance increased by a factor of five possibly due to the rupturing of the conducting channel. On cyclically applying the “SET” and “RESET” biases, the device was switched between low and high resistance states with excellent repeatability. Interestingly, it was also observed that the switching ratio increased on increasing the SET bias making this device a promising candidate for realizing tunable write once read many (WORM) memory devices.

In this paper, we demonstrate thermal bi-stability and hysteresis in hetero-phase molybdenum diselenide (h-MoSe2) consisting of 2H semiconducting MoSe2 and molybdenum oxide (MoOx) phases. h-MoSe2 exhibits pinched hysteresis in the current-voltage characteristics, with the lobe area increasing with decreasing temperature. High and low resistance states were encoded into the sample by thermal manipulation. Cooling the sample below room temperature (RT) drives it to a low resistance state (“1” state), whereas heating above RT switches it to a high resistance state (“0” state). The ratio between “1” and “0” resistance states was found to be greater than 2000 with arbitrary long retention time at room temperature. The results are discussed in terms of temperature-induced adsorption/desorption of water vapor and its interplay with the charge transfer in MoSe2. Our study indicates that h-MoSe2 can be a potential candidate for application in alternate memory devices such as thermal memory and memristors.

The coexistence of negative photoconductivity and metallic-like behavior in conventional semiconductors is very uncommon. In this work, we report the existence of such unconventional physical properties in Molybdenum disulfide nanoflowers (MoS2-NF). This is achieved by making the surface of MoS2 hygroscopic by alcohol treatment and creating a transport channel that favors protonic over electronic conduction. On cooling the MoS2-NF in a heat sink, the excess water that condenses on the surface forms a proton (H3O+) wire which exhibits pinched hysteresis characteristics. The conductivity of MoS2 increased by two orders of magnitude in the proton-dominated conduction regime with an exceptionally high positive temperature coefficient of 1.3×104 Ω/K. Interestingly, MoS2-NF also exhibits strong negative photoresponse (NPC) at room temperature when illuminated with UV and infra-red radiation. This interesting behavior observed in MoS2 NF can be useful for energy harvesting applications and the realization of fast thermal memories and optical switches.