Single ZnO nanocactus gas sensor formed by etching of ZnO nanorod

Abstract

Etching of materials on the nanoscale is a challenging but necessary process in nanomaterials science. Gas sensing using a single ZnO nanocactus (NC), which was prepared by facile isotropic nanoetching of zinc oxide nanorods (NR) grown by chemical vapor deposition (CVD) using an organic photoresist (PR) by a thermochemical reaction, is reported in this work. PR consists of carboxylic acid groups (COOH) and cyclopentanone (C5H8O), which can react with zinc and oxygen atoms, respectively, on the surface of a ZnO NR. The thermochemical reaction is controllable by varying the concentration of PR and reaction time. A gas sensor was fabricated using a single NC. Gas sensing was tested using different gases such as CH4, NH3 and carbon monoxide (CO). It was estimated that the surface area of a ZnO NC in the case of 50% PR was found to increase four-fold. When compared with a single ZnO NR gas sensor, the sensitivity of a ZnO NC was found to increase four-fold. This increase in sensitivity is attributed to the increase in surface area of the ZnO NC. The formed single ZnO NC gas sensor has good stability, response and recovery time.

Fabrication of ZnO Nanobrushes by H2–C2H2 Plasma Etching for H2 Sensing Applications

“…Similar improvements in gas response, although less pronounced, have been found when varying the aspect ratio of ZnO nanorod arrays or by fabricating cactus-like ZnO nanostructures …”

“…It is thus expected that the process is self-reinforcing where initial surface features and/or crystallographic defects such as oxygen vacancies are being enhanced by preferential etching. The fact that similar self-patterning behavior of single crystalline, wurtzite type ZnO microrods was found for a different etching mechanism 30 ZnO crystals themselves as the source for the observed patterning.…”

“…Similar improvements in gas response, although less pronounced, have been found when varying the aspect ratio of ZnO nanorod arrays 9 or by fabricating cactus-like ZnO nanostructures. 30 The influence of the Si/SiO x layer formed during plasma etching has been investigated by fabrication of a turned over sensor device showing that the surface of the nanobrush covered by SiO x does not contribute to the measured gas response. Thus, the ZnO nanowire arrays are solely responsible for the functionality of the sensors.…”

“…In particular, the formation of hierarchical or nano-on-micro structures, e.g., via etching 28 or growth processes, 29 is of great interest. Cactus- 30 or tree-like 31 morphologies on the nanoscale have been fabricated. Such nano-on-micro structures possess large surface areas and are thus well suited for applications such as gas sensing.…”

Hydrogen gas sensing using aluminum doped ZnO metasurfaces

“…[9][10] As losses are inherent to the plasmonic substance, alternative materials with lower optical losses result in being more suitable for sensing platforms. Zinc oxide (ZnO)-based nanostructures, 11 as a dielectric material, have been studied extensively for highly sensitive, selective and efficient gas sensors for the detection of various hazardous and toxic gases such as NO, NO 2 , [12][13] H 2 , [14][15] ammonia (NH 3 ), 16 methane (CH 4 ), [16][17] acetone, 18 ethanol, [19][20][21][22] humidity, 23 CO, 16,[24][25][26] volatile organic compound (VOCs), 27 and hydrogen. 17,[28][29][30][31][32][33][34][35][36][37][38] According to the literature, ZnO holds the promise to develop technologies based on resistive-type gas sensor for electrical readout.…”