Lateral electrical transport, optical properties and photocurrent measurements in two-dimensional arrays of silicon nanocrystals embedded in SiO2

In this study we investigate the electronic transport, the optical properties, and photocurrent in two-dimensional arrays of silicon nanocrystals (Si NCs) embedded in silicon dioxide, grown on quartz and having sizes in the range between less than 2 and 20 nm. Electronic transport is determined by the collective effect of Coulomb blockade gaps in the Si NCs. Absorption spectra show the well-known upshift of the energy bandgap with decreasing NC size. Photocurrent follows the absorption spectra confirming that it is composed of photo-generated carriers within the Si NCs. In films containing Si NCs with sizes less than 2 nm, strong quantum confinement and exciton localization are observed, resulting in light emission and absence of photocurrent. Our results show that Si NCs are useful building blocks of photovoltaic devices for use as better absorbers than bulk Si in the visible and ultraviolet spectral range. However, when strong quantum confinement effects come into play, carrier transport is significantly reduced due to strong exciton localization and Coulomb blockade effects, thus leading to limited photocurrent

Dependence of the radiative recombination lifetime upon electric field in silicon quantum dots embedded into

The influence of the electric field on the radiative recombination of an electron-hole pair in a silicon quantum dot is assessed by means of a variational calculation. In contrast with III-V devices, in the case of silicon the use of \ab{SiO_2} as a matrix makes possible the application of very large electric fields, which should indeed have a considerable impact on the radiation lifetime. For a distribution of crystallites, a growing electric field should lead to a quenching of the radiative recombination in the larger dots and to a noticeable shift of the spectrum

A Novel Thermal Position Sensor Integrated On A Plastic Substrate

Microelectromechanical systems (MEMS), printed-circuit board (PCB), Temperature detection, motion sensorA thermal position sensor was fabricated and evaluated. The device consists of an array of temperature sensing elements, fabricated entirely on a plastic substrate. A novel fabrication technology was implemented which allows direct integration with read out electronics and communication to the macro-world without the use of wire bonding. The fabricated sensing elements are temperature sensitive Pt resistors with an average TCR of 0.0024/C. The device realizes the detection of the position and the motion of a heating source by monitoring the resistance variation of the thermistor array. The application field of such a cost-effective position sensor is considered quite extensive

Simple method for determining Si p-n junction depth using anodization

A simple method for the determination of a Si p+/n junction depth is presented. The method is designed to delineate the specific junction due to its importance in the field of Si solar cells where cost effective and fast characterization techniques are necessary. It consists of the electrochemical transformation of the p+ Si to porous Si. The determination of the porous Si depth with the use of cross-sectional Scanning Electron Microscope (SEM) images provides a direct, fast and easy to implement measurement of the junction depth. In addition, through a simple 4-point probe electrical measurement of the sheet resistance, the average dopant concentration is determined, which allows the creation of an abrupt junction approximation of the p+/n junction. The method is shown to produce accurate results in two types of doping techniques, namely implantation and spin-on-doping and a range of junction depths between 200 nm and 1500 nm, as compared to the well-established secondary ion mass spectrometry (SIMS) technique