Surface effects in metal oxide-based nanodevices

Abstract

As devices shrink to the nanoscale, surface-to-volume ratio increases and the surface-environment interaction becomes a major factor for affecting device performance. The variation of electronic properties, including the surface band bending, gas chemisorption or photodesorption, native surface defects, and surface roughness, is called "surface effects". Such effects are ambiguous because they can be either negative or beneficial effects, depending on the environmental conditions and device application. This review provides an introduction to the surface effects on different types of nanodevices, offering the solutions to respond to their benefits and negative effects and provides an outlook on further applications regarding the surface effect. This review is beneficial for designing nano-enabled photodetectors, harsh electronics, memories, sensors and transistors via surface engineering.

Ultrahigh, Ultrafast, and Self‐Powered Visible‐Near‐Infrared Optical Position‐Sensitive Detector Based on a CVD‐Prepared Vertically Standing Few‐Layer MoS2/Si Heterojunction

“…The high response speed of the V‐MoS 2 /Si heterojunction as a PSD can be mainly ascribed to the following three probable reasons. The first is that the quality of the CVD‐prepared MoS 2 is very high with relatively fewer defects/traps, and the Si substrate is extensively cleaned with a new thin SiO 2 passivation layer on it; thus, the defect recombination in the bulk and interface can be largely reduced as these defects is suggested to have significantly influence on the photoelectric properties 26. The second is that the distinct vertically standing few‐layer structure of the MoS 2 film can greatly facilitate the longitudinal transport of photogenerated carriers along the intralayer direction to the top collection electrode, resulting in high response speed and large LPV.…”

“…To date, various van der Waals heterostructures and lateral heterostructures have been prepared and successfully applied in photodetectors,17, 22 field‐effect transistors,23 photocatalysts,24 and solar cells 16, 25. However, large‐area defect‐free monolayer MoS 2 has not yet been widely demonstrated and accurate transfer and positioning cannot be well achieved, making it difficult to utilize for large‐scale and high‐quality device applications as surface effects, such as surface band bending, surface roughness, photodesorption, gas chemisorption, and surface related defects or states, have significantly important effects on the photoelectric properties of 2D materials 26. Additionally, monolayer or few‐layer MoS 2 can only absorb a small portion of incident light due to its ultrathin thickness, and its excellent optical absorption property cannot be well developed, thus restricting photocurrent (/photovoltage) improvement in MoS 2 ‐based devices.…”

Surface effects of electrode-dependent switching behavior of resistive random-access memory

“…The concentration of chemisorbed O À 2ðadÞ at the surface of metal oxides at room temperature is greater in air compared to vacuum. 17,18 Our results in Fig. 2 show that the devices tested under air had a higher switching probability compared to the same ReRAM devices tested under vacuum, which suggests that a higher O À 2ðadÞ concentration leads to a higher switching probability.…”

“…17,18 The ambient sensitivity of ZnO can be further increased using Pt or Au nanoparticles; a finding which is attributed to the fact that Pt and Au serve as catalysts to lower the activation energy for both the desorption/adsorption processes. [20][21][22] In addition, gas sensors made using Pt/ ZnO stacks, with capping layers on the edges of the Pt top electrodes, show that the ambient environment can directly affect the chemisorption process at the ZnO surface through the Pt layer due to the high mobility of oxygen within Pt.…”

“…The second mechanism that may cause the device's electrode dependent resistance is chemisorption from the ambient environment, which tends to capture free electrons at the surface and form a lowconductivity depletion layer near the surface of the metal oxide to reduce the IS and HRS resistance of the ReRAM. 17 In order to determine the origin of the electrode dependence, we measured the resistance of the ZnO ReRAM device under different ambient environments. Fig.…”