The first characterization of the low-frequency noise in a self-aligned Si/SiGe heterojunction bipolar transistor (HBT) is reported. The observed low-frequency noise exhibits a pure 1/f shape, probably related to carrier number fluctuations at the pseudomorphic emitter-base heterointerface.

This Letter reports experimental observations regarding the significant changes in the transmission modulus and phase of the propagating microwave signals up to 110 GHz in a micromachined coplanar waveguide supported on a dielectric membrane with a thickness of 1.4 μm filled with a mixture of carbon nanotubes when exposed to nitrogen gas. These large shifts of amplitude and phase of microwave signals due to gas absorption represent the experimental basis on which a miniature wireless gas sensor could be implemented.

In this study, two different characterization techniques based on Kelvin probe force microscopy (KPFM) have been used to investigate the dielectric and substrate charging in electrostatic micro- and nano-electromechanical systems (MEMS and NEMS). The first technique (KPFM-MEMS) has been employed to study the discharging process on a microscopic scale in a charged MEMS dielectric film. This has been performed by monitoring the surface potential decay with time of charged PECVD silicon nitride films implemented in electrostatic capacitive MEMS switches. The second methodology, KPFM-thin films (KPFM-TF), has been applied to investigate the charging/discharging processes in bare SiNx films as well as the substrate charging phenomenon. It makes use of the atomic force microscope tip to simulate charge injection through a single asperity, and then measure the induced surface potential. The influence of the SiNx film thickness and deposition conditions has been studied. Moreover, the impact of bias amplitude and bias polarity applied during charge injection has been explored. Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy material characterization techniques have been used to determine the chemical bonds and compositions, respectively, of the SiNx films being investigated. The nanoscale KPFM results obtained in this study reveal an accurate understanding of both the dielectric charging and the substrate charging that take place in electrostatic MEMS/NEMS devices.

A new and efficient digital baseband architecture for impulse radio ultra-wideband (IR-UWB) transceivers with reconfigurable capacities for wireless sensor network applications is presented. An implementation has been made on FPGA for validation by measurements. It is believed to achieve the highest data rate and the largest number of operating modes for an IR-UWB reconfigurable transceiver. Measurements demonstrate reconfigurability in data rate (from 4 to 125 Mbits/s), chip duration (from 8 to 32 ns), pulse duration (from 1 to 4 ns), bit duration (from 8 to 256 ns), processing gain (from 1 to 8 pulses/bit), occupied bandwidth, radio range, BER performance, synchronisation accuracy (from 0.5 to 4 ns), pulse amplitude, transmitted power density, duty cycle (from 3 to 50%), power consumption, spectrum occupation, and maximum supported UWB channel delay spread (from 4 to 31 ns).