Potential barrier height at the grain boundaries of a poly-silicon nanowire

We present measurements of the potential barrier height and its dependence on grain size in poly-silicon nanowire (P-SiNW) arrays. Measurements conducted using Kelvin probe force microscopy coupled with electrostatic simulations, enabled us also to extract the density of the grain boundary interface states and their energy distribution. In addition it was shown that the barrier height scales with the grain size as the square of the grain radius

Recent Advances in Silicon FET Devices for Gas and Volatile Organic Compound Sensing

Highly sensitive and selective gas and volatile organic compound (VOC) sensor platforms with fast response and recovery kinetics are in high demand for environmental health monitoring, industry, and medical diagnostics. Among the various categories of gas sensors studied to date, field effect transistors (FETs) have proved to be an extremely efficient platform due to their miniaturized form factor, high sensitivity, and ultra-low power consumption. Despite the advent of various kinds of new materials, silicon (Si) still enjoys the advantages of excellent and reproducible electronic properties and compatibility with complementary metal–oxide–semiconductor (CMOS) technologies for integrated multiplexing and signal processing. This review gives an overview of the recent developments in Si FETs for gas and VOC sensing. We categorised the Si FETs into Si nanowire (NW) FETs; planar Si FETs, in which the Si channel is either a part of the silicon on insulator (SOI) or the bulk Si, as in conventional FETs; and electrostatically formed nanowire (EFN) FETs. The review begins with a brief introduction, followed by a description of the Si NW FET gas and VOC sensors. A brief description of the various fabrication strategies of Si NWs and the several functionalisation methods to improve the sensing performances of Si NWs are also provided. Although Si NW FETs have excellent sensing properties, they are far from practical realisation due to the extensive fabrication procedures involved, along with other issues that are critically assessed briefly. Then, we describe planar Si FET sensors, which are much closer to real-world implementation. Their simpler device architecture combined with excellent sensing properties enable them as an efficient platform for gas sensing. The third category, the EFN FET sensors, proved to be another potential platform for gas sensing due to their intriguing properties, which are elaborated in detail. Finally, the challenges and future opportunities for gas sensing are addressed

NATO Advanced Study Institute on Scanning Probe Microscopy : Characterization, Nanofabrication and Device Application of Functional Materials

As the characteristic dimensions of electronic devices continue to shrink, the ability to characterize their electronic properties at the nanometer scale has come to be of outstanding importance. In this sense, Scanning Probe Microscopy (SPM) is becoming an indispensable tool, playing a key role in nanoscience and nanotechnology. SPM is opening new opportunities to measure semiconductor electronic properties with unprecedented spatial resolution. SPM is being successfully applied for nanoscale characterization of ferroelectric thin films. In the area of functional molecular materials it is being used as a probe to contact molecular structures in order to characterize their electrical properties, as a manipulator to assemble nanoparticles and nanotubes into simple devices, and as a tool to pattern molecular nanostructures. This book provides in-depth information on new and emerging applications of SPM to the field of materials science, namely in the areas of characterisation, device application and nanofabrication of functional materials. Starting with the general properties of functional materials the authors present an updated overview of the fundamentals of Scanning Probe Techniques and the application of SPM techniques to the characterization of specified functional materials such as piezoelectric and ferroelectric and to the fabrication of some nano electronic devices. Its uniqueness is in the combination of the fundamental nanoscale research with the progress in fabrication of realistic nanodevices. By bringing together the contribution of leading researchers from the materials science and SPM communities, relevant information is conveyed that allows researchers to learn more about the actual developments in SPM applied to functional materials. This book will contribute to the continuous education and development in the field of nanotechnology

Impact of Dopant Compensation on Graded p-n Junctions in Si Nanowires

The modulation between different doping species required to produce a diode in VLS-grown nanowires (NWs) yields a complex doping profile, both axially and radially, and a gradual junction at the interface. We present a detailed analysis of the dopant distribution around the junction. By combining surface potential measurements, performed by KPFM, with finite element simulations, we show that the highly doped (5 × 1019 cm–3) shell surrounding the NW can screen the junction’s built in voltage at shell thickness as low as 3 nm. By comparing NWs with high and low doping contrast at the junction, we show that dopant compensation dramatically decreases the electrostatic width of the junction and results in relatively low leakage currents

Accurate Method To Determine the Mobility of Transition-Metal Dichalcogenides with Incomplete Gate Screening

Van der Waals layered transition metal dichalcogenides, usually exhibit high contact resistance due to the induced Schottky barriers, which occur at non-ideal metal-semiconductor contacts. These barriers usually contribute to an underestimation in the determination of mobility, when extracted by standard, two terminals methods. Furthermore, in devices based on atomically-thin materials, channels with thickness of up to a few layers cannot completely screen the applied gate bias, resulting in an incomplete potential drop over the channel; the resulting decreased field-effect causes further underestimation of the mobility. We demonstrate a method based on Kelvin probe force microscopy, which allows us to extract the accurate semiconductor mobility and eliminates the effects of contact quality and/or screening ability. Our results reveal up to a sevenfold increase in mobility in a monolayer device