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Keywords:

  • field ionization;
  • gas sensors;
  • microstructures;
  • nanowires;
  • silicon;
  • ZnO

In this study, regularly patterned and hierarchically structured silicon (Si) micro-scale pillars and walls with high aspect ratio were fabricated using the deep reactive ion etching (DRIE) process. Dense arrays of ZnO nanowires were hydrothermally grown on the surface of the Si structures subsequent to the deposition of Aluminum–ZnO (AZO) thin films onto the vertically oriented p- and n-type Si micro-scale pillars and walls – resulting in three-dimensional (3D) heterostructures. Electrical and optical measurements of the fabricated pn nano-heterojunctions demonstrate strong capabilities for detecting ultraviolet (UV)–visible (VIS) photons with drastically reduced reflection loss. We also demonstrate low-voltage sensing of gases using these structures through the field ionization process.