Mixed mode, ionic-electronic diode using atomic layer deposition of V2O5 and ZnO films

Abstract

We demonstrate high current rectification in a new system comprising 30 nm of hydrated vanadium pentoxide and 100 nm of zinc oxide (V 2 O 5 $nH 2 O-ZnO) thin film structures. The devices are prepared using a low temperature (<150 C), all atomic layer deposition process. A key element in the rectifying properties comes from anomalous p-type conductivity in V 2 O 5 -an otherwise well known n-type semiconductor. Experimental evidence points to protonic (H + ) conductivity due to intercalated water in V 2 O 5 as the source for p-type behaviour, while the ZnO is known to be electronically n-type. Thus, the diode behaves as a novel, mixed mode ionic-electronic rectifier. Further, we show that the diode characteristics are strongly dependent on the electrode material in contact with V 2 O 5 $nH 2 O. A high I on /I off ratio (598) at AE 2 V is obtained for oxygen-free Pt electrodes, whereas a low I on /I off ratio ( 19) is obtained for oxygen-rich ITO electrodes, suggesting the deleterious effects of oxygen atom reactivity to device characteristics.

Au‐Coated Honeycomb Structure as an Efficient TCO‐Free Counter‐Electrode for Quantum‐Dot‐Sensitized Solar Cells

“…As shown in this Figure, linear I–V curves were obtained for both the forward and reverse bias conditions. These results indicate that the conductivity of the Au‐coated substrates exhibits net ohmic behavior …”

Ozone-Based Atomic Layer Deposition of Crystalline V2O5 Films for High Performance Electrochemical Energy Storage

“…The XPS spectra (Figure 3d) show that vanadium is in a 5+ valence state, with negligible carbon in the films. In contrast, both carbon and water were detected in the amorphous V 2 O 5 films obtained from H 2 O-based ALD process, 15,16,28 We believe the absence of water and carbon residuals in the V 2 O 5 films prepared by O 3 -based ALD is critical for the low temperature crystallization behavior.…”

“…Significant research has been done using vanadyl triisopropoxide (VO(OC 3 H 7 ) 3 , VTOP) as the vanadium precursor and water as the oxidant, an ALD process which yielded amorphous films associated with V 2 O 5 gel formation from water exposure in the process and subsequent ambient exposure. 15 In order to remove the water and crystallize the film, post annealing above 400°C was required, posing limitations for the choice of the substrates for electrodes. Recently, Detavernier et al extended the choices of oxidants to include plasma oxygen in a remote plasma-enhanced ALD process, achieving crystalline V 2 O 5 films.…”

Atomic layer deposition of vanadium oxides: process and application review

“…Unfortunately, these compounds were not investigated as ALD precursors so far. [46][47][48][49][50][51][52][53][54][55][56][57] 3.3. Alkylamide compounds Vanadium (IV) amide complexes are volatile, reactive, produce noncorrosive by-products, and leave marginal impurities in the films, [58].…”