Query: MoS2 field-effect transistor,senor

title: Analyzing the Carrier Mobility in Transition Metal Dichalcogenide MoS2 Field Effect Transistors
abstract: Transition metal dichalcogenides (TMDCs) are an important class of two dimensional (2D) layered materials for electronic and optoelectronic applications, due to their ultimate body thickness, sizable and tunable bandgap, and decent theoretical room temperature mobility. So far, however, all TMDCs show much lower mobility experimentally because of the collective effects by foreign impurities, which has become one of the most important limitations for their device applications. Here, taking MoS2 as an example, the key factors that bring down the mobility in TMDC transistors, including phonons, charged impurities, defects, and charge traps, are reviewed. A theoretical model that quantitatively captures the scaling of mobility with temperature, carrier density, and thickness is introduced. By fitting the available mobility data from literature over the past few years, one obtains the density of impurities and traps for a wide range of transistor structures. It shows that interface engineering can effectively reduce the impurities, leading to improved device performances. For few layer TMDCs, the lopsided carrier distribution is analytically modeled to elucidate the experimental increase of mobility with the number of layers. From our analysis, it is clear that the charge transport in TMDC samples is a very complex problem that must be handled carefully.

title: Reply to "Comment on 'Metal Semiconductor Field Effect Transistor with MoS2/Conducting NiOx van der Waals Schottky Interface for Intrinsic High Mobility and Photoswitching Speed'"
abstract: In a recent article, we reported metal semiconductor fieldeffect transistors (MESFETs) with a few layer MoS2 channel and its intrinsic high mobility, which was supported by Hall effect measurements and photoswitching dynamics. Yang and Liao made a comment on our report. We authors have carefully read the comments and found some misunderstandings which might be from their lack of in depth review on our MESFETs and Hall effect measurements. Following is our response regarding their three main arguments. The first main argument raised by them is regarding electron carrier concentration in our MoS2 channel of the MESFET, which was measured to be 4.03 x 10 cm 2 for N2d (or 2.52 x 10 cm 3 for N3d) Although citing four other reports, Liao et al. claim that N2d of a few layer MoS2 should be 2 orders of magnitude higher than our value even without any gate voltage support, and it may not be acceptable because of two reasons. First of all, previous older papers reported the doping concentration of unintentionally doped thin exfoliated/bulk MoS2 as ~10 cm 3 for N3d (10 10 cm 2 for N2d) Moreover, two among four reports cited by Yang and Liao show that the metal insulator field effect transistor (MISFET) devices were supported by positive gate bias. According to ref 8, where Hall measurement on a few layer MoS2 MISFET channel with a 285 nm thick SiO2/p Si universal back gate was conducted, Hall measurement could not be carried out without positive voltage back gating because good ohmic contact between the electrode and few layer MoS2 is not possible without electron accumulation by back gate support. That is why we used mechanically exfoliated, 16 nm thick MoS2 on the glass substrate for Hall measurements. As a result, we could obtain a maximum carrier concentration of 2.52 x 10 cm 3 for N3d at room temperature and also confirmed that the electron concentration decreases with the measurement temperature decrease. The second argument by Liao et al. is basically the same as their first argument, pointing out that we used 2 orders of magnitude lower N2d for mobility calculation. However, here they add more mistakes for the mobility calculation, equating MISFETs of 0 gate voltage status with our MESFET device.

title: Research progress of molybdenum disulfide field effect transistor biosensors
abstract: The 2D MoS2 FET biosensor has the advantages of small size, low power consumption, ultra fast response, ultra low detection limit, high sensitivity, and well integrated circuit compatibility. For now, many 2D MoS2 FET biosensors have been developed for the detection of various types of analytes. In this paper, the research progress of 2D MoS2 FET biosensors in recent years is reviewed, and the prospects and trends in this field are given in combination with the current challenges.

title: Advances in MoS2 Based Field Effect Transistors (FETs)
abstract: This paper reviews the original achievements and advances regarding the field effect transistor (FET) fabricated from one of the most studied transition metal dichalcogenides: two dimensional MoS2. Not like graphene, which is highlighted by a gapless Dirac cone band structure, Monolayer MoS2 is featured with a 1.9 eV gapped direct energy band thus facilitates convenient electronic and/or optoelectronic modulation of its physical properties in FET structure. Indeed, many MoS2 devices based on FET architecture such as phototransistors, memory devices, and sensors have been studied and extraordinary properties such as excellent mobility, ON/OFF ratio, and sensitivity of these devices have been exhibited. However, further developments in FET device applications depend a lot on if novel physics would be involved in them. In this review, an overview on advances and developments in the MoS2 based FETs are presented. Engineering of MoS2 based FETs will be discussed in details for understanding contact physics, formation of gate dielectric, and doping strategies. Also reported are demonstrations of device behaviors such as low frequency noise and photoresponse in MoS2 based FETs, which is crucial for developing electronic and optoelectronic devices.

title: 2D Material Channel Field Effect Transistor for VLSI
abstract: 2D materials have attracted tremendous attention for a variety of properties such as ultra low body thickness, ultra high mobility, tunable bandgap, etc. These unique merits of the 2D materials bring in the significant improvements and new perspectives in the digital CMOS scaling, analog performance, as well as the 3D integration of the wafer stacking. In this dissertation, two kinds of 2D materials, namely the graphene and molybdenum disulfide(MoS2) have been closely examined through material synthesis, device simulation and performance optimization. Among these 2D materials, graphene is well known for its high mobility and high saturation velocity, which makes it a promising candidate in the analog device, where high transconductance and cut off frequency is mostly appreciated. To integrate of such device into the traditional Complementary Metal Oxide Semiconductor(CMOS) technology, the chemical vapor deposition of graphene sheet is reviewed and studied as a viable synthesis method. The growth of graphene using copper as catalyst has been carried out using a resistive heating tube furnace. The Raman spectra of the thin film synthesized on the copper foil, blanket copper film and patterned copper dots are demonstrated and analyzed. It is found that the concentration of copper vapor plays a critical role in the quality of deposited graphene film. In addition, the copper vapor catalyzed growth directly on the insulating film has been reported and fabricated into device. Simulation on the field effect transistor(FET) using graphene as channel is carried out based on the drift diffusion model. Simulated characteristics are compared with the experimental results based on the extracted value. By using the contact resistance model, it is found that the source/drain resistance shows substantial impact on the on state current of the transistor. This is because the voltage drop on the resistance dominates the carrier concentration in the pinch off region, which limits the on current. In order to improve the contact resistance, three different metal contacts have been adopted for graphene transistor, from which, the contact resistivity is extracted with its transfer characteristic. Among Ti, Ni and Pd, palladium shows the lowest contact resistivity to graphene around 5e 6 Ohm cm^2. Meanwhile, the carbon layer directly deposited on SiO2 substrate is examined by its transfer characteristic. The similar transconductance but different level of the drain current, shows that longer deposition time only increases the thickness of the carbon layer rather than the mobility. Unlike graphene, MoS2 with reasonable band gap and the ultra thin body exhibits its potential in improving the short channel effect, and in return, increasing the on current. Nevertheless, the simulation on the MoS2 transistor under drift diffusion model shows otherwise down to the physical channel length of 10nm. Though MoS2transistor improves the short channel behavior, such as Drain Induced Barrier Lowering (DIBL) and Subthreshold Swing (SS) the on current of the MoS2 transistor shows no increase in comparison with strained Silicon On Insulator (sSOI) device and FinFET structure during the brutal force scale down of gate length. However, MoS2 can still be a promising candidate to thin film transistor and an option in the 3D integration for integrated circuits. The synthesis of MoS2 is achieved through the sulfidation of pre deposited MoO3 film on the insulating substrate. A post sulfidation process is adopted to improve the quality of 2D material, which is closely related to the duration (shown by the sheet resistance in transmission line structure) The effect of rapid thermal annealing(RTA) on metal to MoS2 contact is demonstrated by the I V curve of the transmission line structure before and after RTA process. The improved linearity shows the elimination of the gap between the metal and semiconductor. Meanwhile, different metals have been deposited as the source/drain and the contact resistances are extracted, where Ti/Au shows better overall resistance. The non linearity between the resistance and channel length is explained and fitted by the transmission line structure on low doped SOI (silicon on insulator) The performance of MoS2 FET has been demonstrated using Ti/Au contact.

title: A wafer scale synthesis of monolayer MoS2 and their field effect transistors toward practical applications
abstract: Molybdenum disulfide (MoS2) have attracted considerable research interest as a promising candidate for downscaling integrated electronics due to the special two dimensional structure and unique physic chemical properties. However, it is still challenging to achieve large area MoS2 monolayers with desired material quality and electrical properties to fulfill the requirement for practical application. Recently, a variety of investigations have focused on wafer scale monolayer MoS2 synthesis with high quality. The 2D MoS2 field effect transistors (MoS2 FET) array with different configurations utilizes the high quality MoS2 film as channels and exhibits favorable performance. In this review, we illustrated the latest research advances in wafer scale monolayer MoS2 synthesis by different methods, including Au assisted exfoliation, CVD, thin film sulfurization, MOCVD, ALD, VLS method and thermolysis of thiosalts. Then an overview of MoS2 FET developments was provided based on large area MoS2 film with different device configurations and performances. The different applications of MoS2 FET in logic circuits, basic memory devices and integrated photodetectors were also be summarized. Lastly we considered the perspective and challenges based on wafer scale monolayer MoS2 synthesis and MoS2 FET for developing practical application in integrated electronics and flexible optoelectronics.

title: PHYSICAL REVIEW APPLIED 10 064029 2018 Correlating Electronic Transport and 1 f Noise in MoSe 2 Field Effect Transistors
abstract: Two Dimensional Transition Metal Dichalcogenides (2D TMDCs) such as MoS2, MoSe2, WS2, and WSe2 with van der Waal's type interlayer coupling are being widely explored as channel materials in a Schottky Barrier Field Effect Transistor (SB FET) configuration. While their excellent electrostatic control and high on/off ratios have been identified, a clear correlation between electronic transport and the lowfrequency noise with different atomic layer thickness is missing. For multilayer channels in MoS2 FETs, the effects of interlayer coupling resistance on device conductance and mobility have been studied, but no systematic study has included interlayer effects in consideration of the intrinsic (channel) and extrinsic (total device) noise behavior. Here, we report the 1/f noise properties in MoSe2 FETs with varying channel thicknesses (3 40 atomic layers) Contributions of channel vs access/contact regions are extracted from current voltage (transport) and 1/f noise measurements. The measured noise amplitude shows a direct crossover from channelto contact dominated noise as the gate voltage is increased. The results can be interpreted in terms of a Hooge relationship associated with the channel noise, a transition region, and a saturated high gate voltage regime whose characteristics are determined by a voltage independent conductance and noise source associated with the metallurgical contact and the interlayer resistance. Both the channel Hooge coefficient and the channel/access noise amplitude decrease with increasing channel thickness over the range of 3 15 atomic layers, with the former remaining approximately constant and the latter increasing over a range of 20 40 atomic layers. The analysis can be extended to devices based on other TMDCs.

title: Research progress and challenges of two dimensional MoS 2 field effect transistors
abstract: This review paper gives an outline of the recent research progress and challenges of 2D TMDs material MoS2 based device, that leads to an interesting path towards approaching the electronic applications due to its sizeable band gap. This review presents the improvement of MoS2 material as an alternate to a silicon channel in a transistor with its excellent energy band gap, thermal conductivity, and exclusive physical properties that are expected to draw attention to focusing on semiconducting devices for most futuristic applications. We discuss the band structure of MoS2 for a different number of layers with its structure, and various synthesis techniques of the MoS2 layer are also reviewed. The MoS2 based field effect transistor has attracted a great deal of attention due to its excellent properties such as mobility, on/off current ratio, and maximum on current of the devices. The transition of mobility as a function of temperature and thickness dependence are also discussed. However, the mobility of MoS2 material is large in bulk form and lower in monolayer form. The use of a high k gate dielectric in MoS2 FET is used to enhance the mobility of the device. Different metal contact engineering and different doping techniques were deployed to achieve low contact resistance. This review paper focuses on various aspects of layered TMDs material MoS2 based field effect transistors.

title: Experimentally Measured Field Effect Mobilities for Few Layer van der Waals Materials
abstract: A literature survey of experimentally measured mobility values for the two dimensional materials MoS2, MoSe2, MoTe2, WS2, WSe2, and black phosphorous carried out during 2015.

title: Flexible Molybdenum Disulfide (MoS2) Atomic Layers for Wearable Electronics and Optoelectronics.
abstract: Flexible, stretchable, and bendable materials, including inorganic semiconductors, organic polymers, graphene, and transition metal dichalcogenides (TMDs) are attracting great attention in such areas as wearable electronics, biomedical technologies, foldable displays, and wearable point of care biosensors for healthcare. Among a broad range of layered TMDs, atomically thin layered molybdenum disulfide (MoS2) has been of particular interest, due to its exceptional electronic properties, including tunable bandgap and charge carrier mobility. MoS2 atomic layers can be used as a channel or a gate dielectric for fabricating atomically thin field effect transistors (FETs) for electronic and optoelectronic devices. This review briefly introduces the processing and spectroscopic characterization of large area MoS2 atomically thin layers. The review summarizes the different strategies in enhancing the charge carrier mobility and switching speed of MoS2 FETs by integrating high k dielectrics, encapsulating layers, and other 2D van der Waals layered materials into flexible MoS2 device structures. The photoluminescence (PL) of MoS2 atomic layers has, after chemical treatment, been dramatically improved to near unity quantum yield. Ultraflexible and wearable active matrix organic light emitting diode (AM OLED) displays and wafer scale flexible resistive random access memory (RRAM) arrays have been assembled using flexible MoS2 transistors. The review discusses the overall recent progress made in developing MoS2 based flexible FETs, OLED displays, nonvolatile memory (NVM) devices, piezoelectric nanogenerators (PNGs) and sensors for wearable electronic and optoelectronic devices. Finally, it outlines the perspectives and tremendous opportunities offered by a large family of atomically thin layered TMDs.