Field Effect Transistor Sensors Based on In‐Plane 1T′/2H/1T′ MoTe₂ Heterophases with Superior Sensitivity and Output Signals

Abstract

2D materials, with their extraordinary physical and chemical properties, have gained extensive interest for physical, chemical and biological sensing applications. However, 2D material-based devices, such as field effect transistors (FETs) often show high contact resistance and low output signals, which severely affect their sensing performance. In this study, a new strategy is developed to combine metallic and semiconducting polymorphs of transition-metal dichalcogenides (TMDCs) to solve this critical issue. Such a phase engineering methodology to integrate large-scale and spatially assembled multilayers of 2H MoTe 2 FETs with coplanar metallic 1T′ MoTe 2 contacts is applied. Such in-plane heterophase-based FETs exhibit an ohmic contact behavior with an extremely low contact resistance due to the coplanar and seamless connections between 2H and 1T′ phases of MoTe 2 . These 1T′/2H/1T′ based FETs are successfully demonstrated for detecting NH 3 with high current outputs increased up to microamp levels without using any conventional interdigital electrodes, which is compatible with the current CMOS circuits for practical applications. Furthermore, the as-fabricated sensors can detect NH 3 gas concentrations down to 5 ppm at room temperature. This study demonstrates a new strategy of applying the heterophase MoTe 2 -based nanoelectronics for high-performance sensing applications.

Ohmic contacts of the two-dimensional Ca2N/MoS2donor–acceptor heterostructure

“…In order to address these issues, the following strategies have been proposed: (1) doping the semiconductors to reduce the Schottky barrier width so that the tunneling current exceeds the thermal ion emission current; this is a common method used in the electrical industry at present; [19][20][21][22] (2) changing the SBH by applying strain; for instance, a transition from the Schottky contact to the Ohmic contact occurs in the MoSSe/Ge heterobilayer under tensile strain; 23 (3) employing 2D metals instead of bulk phases as electrodes to suppress the MIGSs; thus, the FLP can be eliminated; [24][25][26][27] (4) phase engineering to reduce the total charge injection barrier, and the phase transformation from semiconductors to metals can reduce the potential barrier of the contacts; [28][29][30] and (5) breaking the vdW gap through an edge-contact geometry. [30][31][32][33] However, how to reduce the contact resistance using feasible strategies, stable performance and wide versatility remains an open question because the above strategies all have inevitable shortcomings.…”

Broad-Band Photodetector Based on a Lateral MoTe2 1T-2H-1T Homojunction

“…They employed the transfer length method to calculate a contact resistance of 470 ± 30 Ω•μm for the 1T′ electrodes. 18 Similarly, Hu and his team employed a phase-selective growth technique to spatially combine 2H MoTe 2 and 1T′ MoTe 2 , resulting in field-effect transistors (FETs) that demonstrated a low contact resistance of 7.1 kΩ•μm at an on-state voltage of −60 V. 19 Jiao and his team created the 1T′/2H MoTe 2 heterostructured shortchannel bilayer field-effect devices using a one-step CVD process, which led to a reduced electrode barrier height of 20 meV and a room-temperature mobility of 130 cm 2 V −1 s −1 . 20 All of these studies have relied on the progress of chemical vapor deposition (CVD) 21 despite the presence of similar initiatives.…”

One-Step Synthesis of Two-Dimensional Metal–Semiconductor Circuitry Based on W-Triggered Spatial Phase Engineering

“…31 Another one-step method for fabricating the in-plane 1T′/2H/1T′ MoTe 2 heterophases was phase-selective growth of specific molybdenum precursors Mo/MoO 3 (where the precursor for 1T′-MoTe 2 growth is a continuous Mo film prepared by electron beam evaporation, and the precursor for 2H-MoTe 2 growth is MoO 3 film prepared by treating Mo film with oxygen plasma). 25 Table S1 further summarized the detailed comparison of large-area fabrication parameters for different growth methods. Existing one-step methods are sensitive to the types of precursors and growth parameters.…”

“…TMD-based 2D metal–semiconductor heterostructures exhibit ohmic contact behavior with low contact resistance, which is an effective approach for high-performance 2D electronics. , Therefore, the phase-controlled synthesis of large-scale 2D metal–semiconductor heterostructures based on TMDs shows promising applications. The existing phase-engineering methods usually suffer from poor spatial controllability, small-scale production, and poor material compatibility. − ,− In addition, most of the 2D metal–semiconductor structures suitable for large-area integration use a two-step chemical vapor deposition (CVD) growth process, − which puts forward high requirements for the secondary growth compatibility of the materials. It is in tight demand to devise a spatially controlled and scalable one-step phase-engineering growth method for directly synthesizing metal–semiconductor heterostructure arrays of TMDs.…”

“…Recently, large-scale 1T′/2H MoTe 2 metal–semiconductor heterostrucutres were obtained by one-step tellurizing MoO 3 /MoO 2.0–2.5 patterns fabricated by a complex process (where the precursor for 1T′-MoTe 2 growth is MoO 3 film deposited by thermal evaporation, and the precursor for 2H-MoTe 2 growth is MoO 2.0–2.5 film obtained by magnetron sputtering of Mo film followed by oxidation) . Another one-step method for fabricating the in-plane 1T′/2H/1T′ MoTe 2 heterophases was phase-selective growth of specific molybdenum precursors Mo/MoO 3 (where the precursor for 1T′-MoTe 2 growth is a continuous Mo film prepared by electron beam evaporation, and the precursor for 2H-MoTe 2 growth is MoO 3 film prepared by treating Mo film with oxygen plasma) Table S1 further summarized the detailed comparison of large-area fabrication parameters for different growth methods.…”