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We report the structural characterization and nanomechanical properties of platinum (Pt) thin films prepared through facile electrochemical synthesis. The Pt thin films were coated onto indium tin oxide (ITO)/glass substrates by two-electrode electrochemical deposition at room temperature. They were characterized using X-ray diffraction, scanning electron microscopy, and atomic force microscopy for structural and morphological analyses. Indentation depth-dependent hardness and elastic modulus of the prepared films were analyzed using the nanoindentation technique. Furthermore, the mechanical properties of the ITO/glass substrates were also investigated to understand the influence of the substrate on the film properties. The prepared films showed reasonable mechanical and structural properties suitable for device applications. Finally, the photoconductivity effect of the prepared Pt film was also studied to determine its suitability for device applications. The Pt film was also coated on Cu plates to check substrates effects on this electrochemical deposition, and found that the Cu plates produced well adherent smooth films.

In this paper, we designed and tested of the passive millimeter-wave imaging system in near range. The proposed passive millimeter-wave imaging system consists two parts. The first part is a 94 GHz band millimeter imaging sensor which is coupled to an antenna, two LNAs, and a diode detector. The second part is a control unit. The control unit is consists of the 2-axes Cartesian robot, the data acquisition (DAQ), and imaging program. The 2-axes Cartesian robot should be able to scan a 2-D image of the metalic tools, IC card and plastic objects, with a raster scanning method. The passive millimeter-wave image of pixels is acquired within less than 60s, and is immediately displayed and stored for post processing.In order to improve the image quality, interpolation methods are applied.

Organic thin film transistors were fabricated using evaporated zinc phthalocyanine as the active layer. Parylene film prepared by chemical vapour deposition was used as the organic gate insulator. The annealing of the samples was performed at 120 °C for 3 h. At room temperature, these transistors exhibit p-type conductivity with field-effect mobilities ranging from 0·025–0·037 cm2/Vs and a (Ion/Ioff) ratio of ∼103. The effect of annealing on transistor characteristics is discussed.

We report an efficient method for growing NiO nanostructures by oblique angle deposition (OAD) technique in an e-beam evaporator for supercapacitor applications. This facile physical vapor deposition technique combined with OAD presents a unique, direct, and economical route for obtaining high width-to-height ratio nanorods for supercapacitor electrodes. The NiO nanostructure essentially consists of nanorods with varying dimensions. The sample deposited at OAD 75° showed highest supercapacitance value of 344 F/g. NiO nanorod electrodes exhibits excellent electrochemical stability with no degradation in capacitance after 5000 charge–discharge cycles. The nanostructured film adhered well to the substrate and had 131% capacity retention. Peak energy density and power density of the NiO nanorods were 8.78 Wh/kg and 2.5 kW/kg, respectively. This technique has potential to be expanded for growing nanostructured films of other interesting metal/metal oxide candidates for supercapacitor applications.

A W-band coplanar waveguide (CPW) low-loss annular branch-line bandpass filter for planar integrated millimeter-wave circuits is presented. It is designed by using the annular branch-line coupler as a transversal filtering section by loading the coupled ports of the coupler with suitable open load stubs and taking the isolated port as the output node. The proposed W-band bandpass filter shows very good performance, insertion-loss of 0.7 dB with a 14.9% of 3 dB relative bandwidth at center frequency of 94 GHz and return loss is better than −27 dB at the center frequency. The designed and fabricated bandpass filter exhibits the good performance for monolithic integrated millimeter-wave circuit applications. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2400–2403, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26264

Using a coplanar waveguide (CPW) feed with a short-circuiting stub, the fed circular slot antenna for W-band operation is presented.The obtained results show that the impedance bandwidth, which is determined by 10 dB return-loss of the proposed slot antenna, can reach to 21% with the center frequency at 94 GHz (80 GHz–100 GHz), and the gain achieves 3.05 dBi at 92 GHz with good radiation performance. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2298–2302, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26284

Synthesis of linked ZnO micro rods by microwave radiation and its characterization is presented in this report. In this simple microwave assisted solution phase route zinc nitrate and hexamethylenetetramine has been used as the starting materials for the synthesis of linked ZnO rods. Linked ZnO rods with various morphologies such as bipods, tripods, tetrapods and etc have been prepared. The influence of irradiation time of microwave on the formation of linked ZnO rods was investigated. X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), and energy dispersive spectroscopy (EDS) were used for the characterization of the product. The FESEM images showed ZnO rods of diameter in the range of 100-200 nm and length around 5000 nm. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This report presents the results of the novel fabrication of 4H-SiC pillars with nanopores using ICP-RIE dry etching. Cl 2 /Ar gas plasma with various mass flow rates was used in this etching process to produce SiC nanopillars without using patterned etch mask. Cylindrical pillars of 300 nm diameter and 500 nm height with smooth side walls were etched on SiC wafer. The etching condition for the optimized fabrication of SiC nanopillars is presented in this report. Each nanopillar has been produced with a nanosize pore at the center along its length and up to the middle of the cylindrical nanopillar; it is a unique feature has not ever been reported in case of SiC. Inclusion of oxygen was found influence the formation of nanopillars by the effect of SiO 2 micro masking. The formation of self assembled SiO 2 layer and its micro masking effect in the fabrication of this unique nanostructure has been investigated using TEM, STEM and EDAX measurements.

In this paper, we show negative differential resistance (NDR) in CdSe quantum dot/MEH-PPV based nanocomposite multi-layer heterostructures at room temperature. The four-layer structure exhibited a maximum peak-to-valley ratio of current of 1190 at room temperature, while two-layer structures show a value of 4. Two-, three- and four-layer structures are studied. Each device configuration exhibits different kind of negative differential resistance. The possible mechanism is explained on the basis of tunneling phenomena.

Electrochemical deposition and characterization of CdSeTe thin film has been presented in this work. CdSexTe1−x (0 < x < 1) compound thin films have been electrodeposited cathodically on SnO2 conducting glass slides using various pH values and deposition potentials using an electrolyte bath solution consisting of CdSO4, SeO2 and TeO2 at different temperatures. The composition in the films has been found to vary linearly with the composition in the bath solution. The increase of selenium content ‘x’ in the CdSexTe1−x films has increased the band gap of the film. Photoelectrochemical solar cell studies were done and its response with concentration of Se was studied and these results have been discussed in this report. © 2010 Elsevier B.V. All rights reserved.

An embedded based system for the measurement of dielectric constant spectroscopy (for frequencies 1 kHz, 10 kHz, 100 kHz, 1 MHz and 10 MHz) for liquids has been designed and developed. It is based on the principle that the change in frequency of an MAX 038 function generator, when the liquid forms the dielectric medium of the dielectric cell, is measured with a microcontroller. Atmel’s AT89LP6440 microcontroller is used in the present study. Further, an LCD module is interfaced with the microcontroller in 4-bit mode, which reduces the hardware complexity. Software is developed in C using Keil’s C-cross compiler. The instrument system covers a wide range of dielectric constants for various liquids at various frequencies and at different temperatures. The system is quite successful in the measurement of dielectric constant in liquids with an accuracy of ± 0.01 %. The dielectric constant is very dependent on the frequency of their measurement. No one-measurement technique is available, however, that will give the frequency range needed to characterize the liquid sample. The paper deals with the hardware and software details.

We fabricated and examined current limiting effect for InP Gunn diodes with stable depletion layer mode operation of diodes for high efficiency Gunn oscillators. Current limiting at the cathode was achieved by a shallow Schottky barrier at the interface. We discussed fabrication procedure, the results for negative differential resistance and rf tests for InP Gunn diodes. It was shown that the fabricated Gunn diodes have the output power of 10.22dBm at a frequency of 90.13GHz. Its input voltage and corresponding current were 8.55V and 252mA, respectively.

Zinc oxide (ZnO) thin films were grown onto SnO2 coated substrates by using cathodic electrodeposition with an aqueous zinc nitrate (Zn (NO3)2) solution at dierent bath temperatures. The kinetics of the electrodeposition of ZnO films has been investigated in this work. The eects of solution concentrations, and temperature and the electrode potential on the growth of ZnO thin films were investigated. The eects of pH on the structural and characteristics of the ZnO films were also studied in order to establish the optimal growth conditions for electrodeposition of ZnO thin films.

We studied planar graded-gap injector GaAs Gunn diodes designed for operation at 94GHz. Two types of planar Gunn diodes were designed and fabricated. In the first diode, a cathode was situated inside a circular anode with a diameter of 190μm. The distance between the anode and cathode varied from 60μm to 68μm depending on the cathode size. Also, we designed a structure with a constant distance between the anode and cathode of 10μm. In the second diode, the anode was situated inside the cathode for the flip-chip mounting on the oscillator circuits. The fabrication of the Gunn diode was based on ohmic contact metallization, mesa etching, and air-bridge and overlay metallization. DC measurements were carried out, and the nature of the negative differential resistance, the operating voltage, and the peak current in the graded-gap injector GaAs Gunn diodes are discussed for different device structures. It is shown that the structure with the shorter distance between the cathode and anode has a higher peak current, higher breakdown voltage, and lower threshold voltage than those of the structure with the larger distance between the cathode and anode.

We fabricated a compact, 94-GHz log-periodic planar antenna on GaAs substrate. We used millimeter-wave monolithic integrated circuit (MMIC) process technology to fabricate the on-chip antenna. An air-bridge crossover is used to replace the conventional bonded structure for crisscross connection, which is compatible with active devices and circuits. The fabricated antenna chip size is 1.2 times 2.6 mm2 . Measurement results show that this antenna can operate from 87 to 99.5 GHz with its return loss better than -10 dB. At 94 GHz, the log-periodic antenna has a return loss of -11 dB and 4.8 dBi of gain.

We present design and fabrication of a 94 GHz radar sensor module. The 94 GHz sensor module has four components including 94 GHz single balanced diode mixer part, waveguide VCO (voltage controlled oscillator) part, magic tee part and bias PCB part. The 94 GHz single balanced diode mixer is developed on Duroid RT 5880 substrate with DC 1346 Schottky diode. The mixer has advantage of good conversion loss at high LO power and isolation characteristic. 94 GHz single balanced diode mixer has advantage of comparatively easy fabrication. The waveguide VCO consist of GaAs Gunn diode, varactor diode, two-bias post and cavity. The waveguide VCO is operated at 94 GHz. The magic tee has four waveguide arm regions with standard WR-10 and divides output power from VCO. Transmission frequency of 94 GHz MMW sensor module is 93.607 ∼ 94.727 GHz. Bandwidth is 1.12 GHz. 2% linearity range is 680 MHz. Power is 11.03 ∼ 11.47 dBm. Conversion loss about −7 dB at IF 500 MHz

A 94 GHz single balanced mixer in 3-dimension was successfully fabricated. The GaAs-based low loss transmission lines, dielectric-supported air-gapped microstrip lines (DAMLs), have been developed using surface micromachining technology, and the DAML-based hybrid ring coupler is successively fabricated. We have developed the high-performance 94 GHz single balanced active mixer using hybrid ring coupler with 70 nm gate length MHEMT. The mixer showed the conversion loss of 2.5 dB ~ 2.8 dB and isolation characteristics less than −30 dB, in the range of 93.65 GHz ~ 94.25 GHz. These results are the best performances demonstrated from a 94 GHz single balanced mixer utilizing GaAs-based HEMTs in terms of conversion loss as well as isolation characteristics.

Millimeter-wave imaging systems are currently being developed for a wide range of applications, including remote sensing, all-weather aircraft landing, and concealed weapon detection. In this paper, we designed and tested of the passive millimeter-wave imaging system using focal plane approach. The proposed system consists of two parts. The first part is a 94 GHz band millimeter imaging part which is coupled to a dielectric lens, a horn antenna, two low noise amplifiers, and a diode detector. The second part is a control part. The control part consists of 2-axes Cartesian robots, and a 16-bit data acquisition (DAQ). The 2-axes Cartesian robot should be able to scan a 2-D image of the scene, with a raster scanning method. The passive millimeter-wave image of 50 × 50 pixels is acquired, and is immediately displayed and stored for post processing. The experimental results are presented to demonstrate the feasibility of the passive millimeter-wave imaging system. In order to improve the image quality, interpolation methods are applied.

The 94 GHz waveguide VCO using InP Gunn diode was designed and fabricated. The fabricated VCO has excellent linearity of 1.7 % at 680 MHz bandwidth and power flatness of 0.68 dBm, respectively. The LPF is designed under -40 dB at 47 GHz and the resonator is designed for frequency generation at 47 GHz. From the measured results the fabricated waveguide VCO has excellent performances: the bandwidth is 1365 MHz at 93.98 ~ 95.345 GHz and the output power range is from 14.78 dBm to 15.46 dBm. The phase noise is under -100 dBc / Hz at 1 MHz offset.

We developed the improved fabrication technology using the trench method for a graded-gap injector GaAs Gunn diode to avoid the formation of cracks which are caused by the difference in the thermal expansion coefficients between the GaAs epi-layer and the gold integral heat sink. We observed the negative-differential-resistance in the fabricated Gunn diode. The process we developed facilitates further process and handling because of the integral heat sink with thickness of 60 mum. Also, the formation of cracks in GaAs epi-layer was reduced during ohmic alloy process because of the reduced stress between the epi-wafer and the gold integral heat sink.

In this paper, a design of compact W-band planar Quasi-Yagi antenna is presented. The proposed antenna is fed by 50 Ohm coplanar waveguide with a broad-band balun in order to convert from unbalanced grounded-coplanar waveguide (G-CPW) mode into balanced coplanar strip line (CPS) mode. This antenna is realized on a high dielectric constant substrate, GaAs-relative dielectric permittivity of 12.9, that's compatible with active devices and circuits. Using the truncated ground plane as a reflector, the proposed antenna has a broad relative bandwidth of 18.07% with its return loss better than -10 dB, front to back ratio is 15.6 dB and 6.08 dBi of gain at 94 GHz. This antenna can be widely applied in wireless communication systems, active phased array antenna or millimeter-wave imaging systems.

In this paper, millimeter-wave 94 GHz drive amplifiers based on metamorphic high electron mobility transistors (MHEMTs) were designed and fabricated. The fabricated 100 nm gate length MHEMT devices exhibit DC characteristics with a drain current density of 690 mA/mm and an extrinsic transconductance of 770mS/mm. The current gain cutoff frequency (fT) and the maximum oscillation frequency (fmax) are 185 GHz and 230 GHz, respectively. The matching circuit of amplifier was designed using CPW (coplanar wave-guide) transmission line. The fabricated amplifier shows a good S21 gain of 7.79 dB, an input return loss (S11) of -16.5 dB and an output return loss (S22) of-15.9 dB.

In this paper, we report our recent research works on the W-band waveguide-to-CPW transitions for various MIMIC applications. For this, the transitions operating in a frequency range of 85 ~ 100 GHz are designed, fabricated and characterized. The designed waveguide-to-CPW transition is optimized to achieve low loss by using an EM field solver of HFSS. From the measurement, an insertion of ?2.2 dB and a return loss of ?23.86 dB, respectively, were obtained at 94 GHz. The average insertion loss of waveguide-to-CPW back-to-back transition is ?2.5 dB in a frequency range of 85 ~ 100 GHz.

We have designed and fabricated a low LO power V-band CPW mixer using GaAs PHEMT technology for the application of millimeter-wave wireless communication systems. The mixer was designed using a unique gate mixing architecture to achieve simultaneously a low LO input power, a high conversion gain, and good LO-RF isolation characteristics. The V-band mixer was fabricated using the MIMIC process including 0.1-? GaAs PHEMTs and CPW transmission lines. The V-band mixer exhibited a high conversion gain of 2 dB at a low LO power of 0 dBm. The low LO power and the high conversion gain achieved in this work is among the best ever reported for a V-band mixer.

We introduce an all-inorganic solution processed bipolar nonvolatile resistive memory device with quantum dot/metal-metal oxide/quantum dot structure. The two terminal device exhibits excellent switching characteristics with ON/OFF ratio >103. The device maintained its state even after removal of the bias voltage. The switching time is faster than 50 ns. Device did not show degradation after 1-h retention test at 150 °C. The memory functionality was consistent even after multiple cycles of operation and the device is reproducible. The switching mechanism is discussed on the basis of charge trapping in quantum dots with metal oxide serving as the barrier.

In this work, we have designed and fabricated the GaAs Gunn diodes for a 94 GHz waveguide voltage controlled oscillator (VCO) which is one of the important parts in a frequency modulated continuous wave (FMCW) radar application. For fabrication of the high power GaAs Gunn diodes, we adopted a graded gap injector which enhances the output power and conversion efficiency by effectively removing the dead-zone. We have measured RF characteristics of the fabricated GaAs Gunn diodes. The operating current, oscillation frequency, and output power of the fabricated GaAs Gunn diodes are presented as a function of the anode diameters. The operating current increases with anode diameters, whereas the oscillation frequency decreases. The higher oscillation frequency was obtained from 60 µm anode diameters of the fabricated Gunn GaAs diodes and higher power was obtained from 68 µm. Also, for application of the 94 GHz FMCW radar system, we have fabricated the 94 GHz waveguide VCO. From the fabricated GaAs Gunn diodes of anode diameter of 60 µm, we have obtained the improved VCO performance.