We present a practical vacuum pressure sensor based on the Schottky junction using graphene anchored on a vertically aligned zinc oxide nanorod (ZnO-NR). The constructed heterosystem of the Schottky junction showed characteristic rectifying behavior with a Schottky barrier height of 0.64 eV. The current–voltage (I–V) features of the Schottky junction were measured under various pressures between 1.0 × 103 and 1.0 × 10− 3 mbar. The maximum current of 38.17 mA for the Schottky junction was measured at – 4 V under 1.0 × 10− 3 mbar. The high current responses are larger than those of the previously reported vacuum pressure sensors based on ZnO nanobelt film, ZnO nanowires, and vertically aligned ZnO nanorod devices. The pressure-sensitive current increases with the vacuum pressure and reaches maximum sensitivity (78.76%) at 1.0 × 10− 3 mbar. The sensitivity and repeatability of the Schottky junction were studied by the current–time (I–T) behavior under variation of vacuum pressure. The sensing mechanism is debated from the surface charge transfer doping effect by oxygen chemisorption. The results suggest that this simple graphene/ZnO-NR Schottky junction device may have potential in the fabrication of vacuum pressure sensor with high sensitivity.

A vacuum pressure sensor based on grapheneZnO nanorod Schottky junction
    Abstract
        Graphical abstract
    1 Introduction
    2 Experimental methods
        2.1 Synthesis of CVD graphene film and ZnO-NR
        2.2 Characterization
        2.3 Vacuum pressure Sensor fabrication
    3 Results and discussions
        3.1 Structural and morphological studies
        3.2 Vacuum pressure sensor studies
    4 Conclusion
    References

• P. Sakthivel(Department of Chemistry, Builders Engineering College, Tirupur, Tamil Nadu 638 108, India) | Department of Chemistry, Builders Engineering College, Tirupur, Tamil Nadu 638 108, India
• K. Ramachandran(Department of Chemistry, Builders Engineering College, Tirupur, Tamil Nadu 638 108, India)
• M. Malarvizhi(Department of Chemistry, Sri GVG Visalakshi College for Women, Udumalpet, Tamil Nadu 642 128, India)
• S. Karuppuchamy(Department of Energy Science, Alagappa University, Karaikudi, Tamil Nadu 630 003, India)
• P. Manivel(Centre for Nanotechnology, Erode Sengunthar Engineering College, Erode, Tamil Nadu 638 057, India) Corresponding author