SPECIFIC BEHAVIOUR OF THE BLOOD SEDIMENTATION PROCESSES EXAMINED BY THE ELECTROCHEMICAL IMPEDANCE MICROSENSOR

Electrochemical impedance microsensor for the fast monitoring of the blood sedimentation has been developed. Planar microsensor consisted of the interdigital array of electrodes (IDAE - finger/gap widths of different values from 5/5 μm to 400/400 μm) based on Au or Pt thin films sputtered on Si/SiO2 or ceramic alumina substrates. IDAE microsensor allows time measurements of electrical impedance changes - impedance rates - (at frequencies of order 0.1 kHz and 10 kHz) of small blood drop applied on it. The determination of the impedance rate during sedimentation and the impedance spectrometry at a low-frequency range of order of 1 kHz seems to be very helpful for a quick diagnostics of the health state. In the IDAE microsensor erythrocyte aggregation/rapid settling/packing periods associated with dryperiod are overlapping due to the planar arrangement of dimensions in order of 1-100 μm. The time monitoring of the blood sedimentation (in the range of 10-900 seconds) by the impedance method can distinguish between healthy and cancer state of blood and could serve for the simple long-term diagnostics after the surgical operation or as a screening procedure for early diagnoses

Electrical and structural characterization of AlGaN/GaN field-effect transistors with recessed gate

Performance of AlGaN/GaN heterostructure field-effect transistors (HFETs) with recessed gate was investigated and compared with non-recessed counterparts. Optimal dry etch conditions by plasma assisted Ar sputtering were found for ~6 nm gate recess of a 20 nm thick AlGaN barrier layer. A decrease of the residual strain after the gate recessing (from -0.9 GPa to -0.68 GPa) was evaluated from the photoluminescence measurement. The saturation drain current at the gate voltage VG = 1 V decreased from 1.05 A/mm to 0.85 A/mm after the recessing. The gate voltage for a maximal transconductance (240-250 mS/mm) has shifted from -3 V for non-recessed HFETs to -0.2 V for recessed counterparts. Similarly, the threshold voltage increased after the gate recessing. A decrease of the sheet charge density from 1 x 10 13 cm-2 to4 x 10 12 cm-2 at VG = 0 V has been evaluated from the capacitance measurements. The RF measurements yielded a slight increase of the cut-off frequencies after the gate recessing. All these indicate that the gate recessing is a useful tool to optimize the AlGaN/GaN HFET performance for high-frequency applications as well as for the preparation of normally-off devices

Improved Tolerance against UV and Alpha Irradiation of Encapsulated Organic TFTs

The aim of this work is to investigate the effects of the encapsulation on the robustness against ionizing radiation on organic thin-film-transistors. We analyzed the UV and alpha radiation effects on the threshold voltage, the hole mobility and interface traps

Effects of amorphous Si capping layer on sputtered BaSi2 film properties

Regarded as a promising absorber material for solar cell applications, Barium disilicide (BaSi2) is still confronted with issues related to surface oxidation. Here, we use a-Si.H deposited by plasma-enhanced chemical vapor deposition as capping layer to prevent surface oxidation of sputtered BaSi2 films. Based on crystalline quality and optical properties characterizations, thin a-Si.H capping cannot sufficiently prevent surface oxidation. Conversely, oxidation of a-Si.H layer in turn promotes Ba diffusion and Si isolation. Applying a thicker a-Si.H capping layer (more than 20 nm) can suppress such effect. The multi-materials capping layer can also be regarded as potential strategy to prevent surface oxidation of BaSi2.</p