Nanoscale heterojunction indium oxide/molybdenum disulphide field-effect transistor: A cost-effective wafer scale fabrication with improved performance

• Fabricated low-cost In₂O₃/MoS₂ heterostructure films using RF sputtering. • Demonstrated wafer-scale fabrication for integration of sensor devices. • Achieved uniform crystals and smooth heterostructure surfaces via annealing. • Heterojunction FETs showed 1100 % higher electron mobility. • pH sensors had over 2 × sensitivity over Si-based ion-sensitive FETs. Metal oxide heterojunction thin films are promising building blocks for the fabrication of functional devices in microelectronics, bio-chemical sensors, photovoltaics, and optical displays. However, balancing the large-scale manufacturability with performance, uniformity, and cost-effectiveness remains a significant challenge. Here, we report a wafer-scale fabrication process of bilayer stacks of high-mobility indium oxide and molybdenum disulphide heterojunction thin films and their application for the preparation of high-performance field-effect transistors (FETs). The annealed heterojunction thin film exhibits uniform crystalline structures and good surface roughness across the whole wafer. A simple soft lithography and lift-off process of the heterojunction thin film could produce nanotransistor devices with a remarkable electron mobility enhancement of more than 1100 % compared to indium oxide or molybdenum disulphide single layer devices. The heterojunction FET sensors yielded more than a twofold higher pH sensitivity compared to silicon-based ionic FETs and excellent linearity. These findings coupled with the cost-effective fabrication strategy underscore the potential of indium oxide and molybdenum disulphide heterojunction FET devices.