Corinne Sartel

Characterizations of Ohmic and Schottky-behaving contacts of a single ZnO nanowire

Current-voltage and Kelvin probe force microscopy (KPFM) measurements were performed on single ZnO nanowires. Measurements are shown to be strongly correlated with the contact behavior, either Ohmic or diode-like. The ZnO nanowires were obtained by metallo-organic chemical vapor deposition (MOCVD) and contacted using electronic-beam lithography. Depending on the contact geometry, good quality Ohmic contacts (linear I-V behavior) or non-linear (diode-like) contacts were obtained. Current-voltage and KPFM measurements on both types of contacted ZnO nanowires were performed in order to investigate their behavior. A clear correlation could be established between the I-V curve, the electrical potential profile along the device and the nanowire geometry. Some arguments supporting this behavior are given based on technological issues and on depletion region extension. This work will help to better understand the electrical behavior of Ohmic contacts on single ZnO nanowires, for future applications in nanoscale field-effect transistors and nano-photodetectors.

Metallic core conduction in unintentionally doped ZnO nanowire

The conduction through unintentionally doped ZnO nanowires grown by metalorganic chemical vapor deposition versus temperature (4 to 300 K) and nanowire radius (50 to 175 nm) was investigated. To obtain a reliable picture of the electrical conduction, controlled experimental conditions were used to master the influence of the surrounding environment. Conduction in the nanowires was found to be metallic through the core of the degenerate semiconductor. The origin of the high residual doping level [(1–5) × 1018 cm−3] is discussed in terms of incorporation of impurities during the growth process.

Electron beam dose dependence of surface recombination velocity and surface space charge in semiconductor nanowires

The characterization of nanowires (NWs) often requires the use of scanning electron beam techniques because of their high spatial resolution. However, the impact of the high energetic electron beam on the physical parameters under investigation is rarely taken into account. In this work, a combination of optical and electrical techniques is involved for the measurement of the electron beam dose (EBD) dependence of cathodoluminescence intensity, exciton diffusion length and electrical resistance in ZnO NWs. Large EBD dependences of these key parameters are observed and their reversibility is investigated. The results are discussed in terms of bulk and surface reversible modifications. In particular, the behaviors of surface recombination velocity and surface space charge under electron beam exposure are determined and simulated. This study points out that caution must be taken and experimental protocols must be well defined when measuring physical parameters of NWs using electron beam techniques.