Electronic to protonic conduction switching in Cu₂O nanostructured porous films: the effect of humidity exposure

Abstract

In this paper, we present the first experimental evidence for electronic to protonic conduction switching in p-type semiconducting nanostructured cuprous oxide (Cu2O) porous films when exposed to humidity.

Electronic and Simple Oscillatory Conduction in Ferrite Gas Sensors: Gas-Sensing Mechanisms, Long-Term Gas Monitoring, Heat Transfer, and Other Anomalies

“…This abnormal phenomenon is not well understood but has been observed previously. [2][3][4][5][6][7][8][9][10][11][12][13][14]26,27 In addition, increasing the operating temperature even further to 275 °C shows a significant drop in the p-type response to less than 50 in the 10,000 ppm LPG concentration. The activation temperatures of magnesium ferrite (MgCe 0.1 Fe 1.9 O 4 ) are shown in Figure S1 of the Supporting Information file.…”

“…The authors claim at lower humidity (70% RH) the electronic conductivity dominates, while at higher humidity (90% RH), protonic conduction takes over during UV light illumination. The most confusing part is when this process (electronic to protonic conduction) is claimed to be responsible for the material switching conductivity direction as a function of RH, 6 as discussed earlier in the introduction. Elsewhere, this switch of conductivity is due to the material's change from p-to n-type as a function of either gas concentration or temperature.…”

“…It has been observed elsewhere. [4][5][6][7][8][9][10][11][12][13][14][15][16]35,36 The novelty in the current p-to n-type carrier reversal is that it was observed at room temperature with the presence of RH. None of the reports of this phenomenon were at room temperature except our amorphous NiO/Ni(OH) 2 nanoplatelets toward NO gas.…”

“…This abnormality is attributed to the physisorbed formation on top of the chemisorbed oxygen species, hence protonic conduction and inversion layer by many others. [5][6][7][8][9][10][11][12][13][14][15]17 On the other hand, the concentration of the chemisorbed oxygen species was also suspected to change the depletion layer and space charge layer. 34−36 The latter mechanism partly fits our current case.…”

“…Solanki et al 5 described the coexistence of both electronic and protonic conductivities due to RH and ultraviolet light. Dhonge et al 6 associated the current reversal switch to electronic to protonic conduction crossover. None of these observations correspond to the current study or give account of energy dissipation during these crossovers of conductivities.…”