Yong-Han Lin

Four-probe electrical-transport measurements on single indium tin oxide nanowires between 1.5?and?300?K

Single-crystalline indium tin oxide (ITO) nanowires (NWs) were grown by the standard thermal evaporation method. The as-grown NWs were typically 100-300 nm in diameter and a few microm long. Four-probe submicron Ti/Au electrodes on individual NWs were fabricated by the electron-beam lithography technique. The resistivities of several single NWs have been measured from 300 down to 1.5 K. The results indicate that the as-grown ITO NWs are metallic, but disordered. The overall temperature behavior of resistivity can be described by the Bloch-Grüneisen law plus a low-temperature correction due to the scattering of electrons off dynamic point defects. This observation suggests the existence of numerous dynamic point defects in as-grown ITO NWs.

Growth of single-crystalline RuO2 nanowires with one- and two-nanocontact electrical characterizations

Single-crystalline RuO2 nanowires were grown by using a thermal evaporation method. A control of the sizes (width and length) and the length-to-width ratio of the nanowires were achieved by tuning the growth time. A transmission electron microscope–scanning tunneling microscope technique invoking one-nanocontact electrical characterization was adopted to determine the room-temperature resistivity (∼100μΩcm) of the nanowires. An e-beam lithography technique facilitating two-nanocontact measurements was performed to establish the metallic characteristic of individual nanowires. The authors found that a nanocontact may introduce high contact resistance, nonlinear current-voltage characteristics, and even semiconducting behavior in the temperature dependent resistance.

Optical characterization of ZnSe epilayers and ZnCdSe∕ZnSe quantum wells grown on Ge∕Ge0.95Si0.05∕Ge0.9Si0.1∕Si virtual substrates

Several approaches have been employed to grow high-quality ZnSe epilayers on Ge∕Ge0.95Si0.05∕Ge0.9Si0.1∕Si virtual substrates. The ZnSe epilayers were characterized by photoluminescence spectroscopy. Migration enhanced epitaxy and inserting an in situ thermal annealing ZnSe buffer layer effectively reduced the intensity of deep level emissions from the ZnSe epilayer grown on a 6°-tilted Ge∕Ge0.95Si0.05∕Ge0.9Si0.1∕Si virtual substrate. Optimized conditions for growing high-quality ZnSe were used to deposit ZnCdSe∕ZnSe multiple quantum wells on Ge∕Ge0.95Si0.05∕Ge0.9Si0.1∕Si virtual substrates. Photoluminescence spectroscopy revealed quantum-confinement effect in the ZnCdSe multiple quantum wells. The evolution of the exciton emission peak energy and the linewidth as a function of temperature indicate a low density of localized sites in the sample with a well width of 1nm. In the high-temperature regime, the thermal quenching of the excitonic emission intensity from ZnCdSe quantum well structures was governe...

Pressure-induced metallization and resonant Raman scattering in Zn1−xMnxTe

Pressure-induced resonant Raman scattering is adopted to analyze the zone-center optical phonon modes and crystal characteristics of Zn1−xMnxTe (0≦x≦0.26) thin films. The pressure (Pt) at which the semiconducting undergoes a transition to the metallic phase declines as a function of Mn concentration (x) according to the formula Pt(x)=15.7−25.4x+19.0x2 (GPa). Pressure-dependent longitudinal and transverse optical phonon frequencies and the calculated mode Gruneisen parameters were adopted to investigate the influence of Mn2+ ions on the iconicity. The experimental results indicate that the manganese ions tend to increase the iconicity of ZnTe under ambient conditions, whereas an external hydrostatic pressure tends to reduce the iconicity and the bond length of Zn1−xMnxTe.

Studies on the electronic and vibrational states of colloidal CdSe/ZnS quantum dots under high pressures

The electronic and vibrational states of colloidal core/shell CdSe/ZnS quantum dots are studied at room temperature by using high pressure optical measurements. Pressure-induced quadratic variations of lattice constants can be observed clearly from both photoluminescence (PL) and Raman spectra up to ~7?GPa. This quadratic relationship is consistent with the theoretical prediction. The pressure coefficients of linear and quadratic terms are 32?meV?GPa?1, ?1?meV?GPa?2 for PL and 4.2?cm?1?GPa?1, ?0.1?cm?1?GPa?2 for Raman measurements, respectively.

Fluctuation-induced tunneling conduction through RuO2 nanowire contacts

A good understanding of the electronic conduction processes through nanocontacts is a crucial step for the implementation of functional nanoelectronic devices. We have studied the current- voltage (I-V) characteristics of nanocontacts between single metallic RuO2 nanowires and contacting Au electrodes, which were pre-patterned by simple photolithography. Both the temperature behavior of contact resistance in the low-bias voltage ohmic regime and the I-V curves in the high-bias voltage non-ohmic regime have been investigated. We found that the electronic conduction processes in the wide temperature interval 1-300 K can be well described by the fluctuation-induced tunneling (FIT) conduction theory. Taken together with our previous work [Lin et al., Nanotechnology 19, 365201 (2008)], where the nanocontacts were fabricated by delicate electron-beam lithography, our study demonstrates the general validity of the FIT model in characterizing electronic nanocontacts.

Structural order and melting of a quasi-one-dimensional electron system

We investigate the influence of confinement on the positional order of a quasi-1D electron system trapped on the surface of liquid helium. We find evidence that the melting of the Wigner solid (WS) depends on the confinement strength, as well as electron density and temperature. A reentrant solid-liquid-solid transition is observed for increasing electron density under constant electrostatic confinement. As the electron row number

Raman scattering of longitudinal-optical-phonon-plasmon coupling in Cl-doped ZnSe under high pressure

{N}_{y}

Pressure-dependent Raman scattering and photoluminescence of Zn1−xCdxSe epilayers

changes, varying commensurability results in a modulation of the WS order, even when

Superconducting fluctuation magnetoconductance in a tungsten carbide film

{N}_{y}