This PDF file contains the front matter associated with SPIE Proceedings Volume 10175, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

In this paper we present a review of research results and technical accomplishments presented by researchers from technical universities, governmental institutes and research companies during the XIIth Scientific Conference Electron Technology, ELTE 2016. This review is based on materials presented at four topical conference sessions: Microelectronics and Nanoelectronics, Photonics, Materials and Technologies, and Microsystems and also on materials presented by invited speakers at two dedicated sessions. Oral sessions were accompanied by the poster sessions. In effect about 50 papers gathered in this volume reflect the topics discussed at the Conference. A short description of technological and measurement possibilities in the laboratories of Academic Centre for Materials and Nanotechnology and also in the Department of Electronics of the Faculty of Computer Science, Electronics and Telecommunications AGH UST are given.

Two architectures of electron beam tools are presented: single beam MEBES Exara designed and built by Etec Systems for mask writing, and the Reflected E-Beam Lithography tool (REBL), designed and built by KLA-Tencor under a DARPA Agreement No. HR0011-07-9-0007. Both tools have implemented technologies not used before to achieve their goals. The MEBES X, renamed Exara for marketing purposes, used an air bearing stage running in vacuum to achieve smooth continuous scanning. The REBL used 2 dimensional imaging to distribute charge to a 4k pixel swath to achieve writing times on the order of 1 wafer per hour, scalable to throughput approaching optical projection tools. Three stage architectures were designed for continuous scanning of wafers: linear maglev, rotary maglev, and dual linear maglev.

This article presents the innovative integrated testing system FiTest for automatic, quick inspection of printed circuit board assemblies (PCBA) manufactured in Surface Mount Technology (SMT). Integration of Automatic Optical Inspection (AOI), In-Circuit Tests (ICT) and Functional Circuit Tests (FCT) resulted in universal hardware platform for testing variety of electronic circuits. The platform provides increased test coverage, decreased level of false calls and optimization of test duration. The platform is equipped with powerful algorithms performing tests in a stable and repetitive way and providing effective management of diagnosis.

The Silicon-On-Insulator (SOI) CMOS is one of the most advanced and promising technology for monolithic pixel detectors design. The insulator layer that is implemented inside the silicon crystal allows to integrate sensors matrix and readout electronic on a single wafer. Moreover, the separation of electronic and substrate increases also the SOI circuits performance. The parasitic capacitances to substrate are significantly reduced, so the electronic systems are faster and consume much less power. The authors of this presentation are the members of international SOIPIX collaboration, that is developing SOI pixel detectors in 200 nm Lapis Fully-Depleted, Low-Leakage SOI CMOS. This work shows a set of advantages of SOI technology and presents possibilities for pixel detector design SOI CMOS. In particular, the preliminary results of a Cracow chip are presented.

The paper presents the quantification of void formation in lead-free solder joints underneath bottom terminated components (BTCs) through X-ray inspection. Experiments were designed to investigate how void formation is affected by using vacuum in reflow soldering on the example of light emitted diode (LED) packages on metal core printed circuit boards (PCBs). Convection and vapour phase reflow soldering were used for LED assembly. X-ray inspection system analyzed the statistical distribution, mean value, standard deviation and process capability value Cpk of thermal pads coverage for various technological versions of LEDs.

Hafnium Oxide-Nitride films were deposited using reactive magnetron sputtering in O₂/N₂/Ar gas mixture. Deposition was planned according to Taguchi optimization method. Morphology of fabricated layers was tested using AFM technique (R_a=0.2÷1,0 nm). Thickness of HfO_XN_Y films was measured using spectroscopic ellipsometry (t=45÷54 nm). Afterwards MIS structures were created by Al metallization process then layers were electrically characterised using I-V and C-V measurements. This allowed to calculate the electrical parameters of layers such as: flat-band voltage U_FB, dielectric constant K_i, interface state trap density D_it and effective charge Q_eff. Subsequently, deposited HfO_xN_y layers were annealed in PDA process (40 min 400 °C 100% N₂) after which the electrical characterization was performed again.

Interface traps density (N_it) and gate insulator thickness (t_ox) impact on MIS tunnel structure electrical characteristics is discussed in respect to bias voltage range corresponding to inversion in the semiconductor substrate region. Effect of N_it and t_ox on equilibrium and non-equilibrium operation regime of the device is presented. Different models of the small-signal response of interface traps are proposed and discussed in respect to several phenomena related to the traps charging and discharging processes. Presented analysis was performed for the MIS structures with the gate dielectric made of silicon dioxide (SiO₂) and hafnium oxide (HfO_x). The obtained results proved that the surface density of interface traps (N_it) and the insulator thickness (t_ox) have correlated impact on the transition between equilibrium and non-equilibrium operation of the MIS tunnel structures.

This papers presents a classic fully differential operational transconductance amplifier (FDOTA) implemented in industrial 28 nm FD-SOI (Fully-Depleted SOI) technology. A novel approach to minimized the FDOTA offset voltage is proposed. The solution employs the unique feature of FD-SOI technology - back-gate biasing - combined with modern compensation methodology. The proposed method results in considerable design overhead. However, this offset cancellation approach is very effective and allows to improve FDOTA performance when classic techniques reach their limits.

This papers presents a high-speed, latched comparator implemented in industrial 28 nm FD-SOI technology. A novel approach to counter the mismatch is proposed. The solution employs trimming the threshold voltage by means of modulating of back-gate polarization of FD-SOI transistors. The comparator is a first step towards the design of a complete 4-bit FLASH analog-to-digital converter, with a sampling frequency of 10 GHz.

Reverse current of GaN vertical Schottky diodes is simulated using Silvaco ATLAS to optimize the geometry for the best performance. Several physical quantities and phenomena, such as carrier mobility and tunneling mechanism are studied to select the most realistic models. Breakdown voltage is qualitatively estimated based on the maximum electric field in the structure.

This paper presents a model of high frequency capacitance of a SOI MOSCAP. The capacitance in strong inversion is described with minority carrier redistribution in the inversion layer taken into account. The efficiency of the computational process is significantly improved. Moreover, it is suitable for the simulation of thin-film SOI structures. It may also be applied to the characterization of non-standard SOI MOSCAPS e.g. with nanocrystalline body.

Three layer structure of Solid Oxide Fuel Cell (SOFC), where a thin semi-conducting layer of electrolyte separates the anode from the cathode, shows a strong similarity to typical semiconductor devices built on the basis of P-N junctions, like diodes or transistors. On the basis of this similarity, the attempt of application of Shockley’s formula for the expression of a current-voltage relation of SOFC is presented. The proposed approach enables a more accurate estimation of the ion exchange current, than the approach based on the Tafel’s formula.

VESTIC technology is an alternative for traditional CMOS technology. This paper presents first measurement data of prototypes of VES-BJT: bipolar transistors in VESTIC technology. The VES-BJT is a bipolar transistor on the SOI substrate with symmetric lateral structure and both emitter and collector made of polysilicon. The results indicate that VES-BJT can be a device with useful characteristics. Therefore, VESTIC technology has the potential to become a new BiCMOS-type technology with some unique properties.

In this work we present the investigations aimed at the optimization of the technology of Reactive Ion Etching in sulfur hexafluoride (SF₆) plasma of silicon, which is necessary during fabrication of TFET according to the original concept of the device designed at Institute of Microelectronics and Optoelectronics (IMiO) of Warsaw University of Technology (WUT) laboratory. We have performed a two-stage optimization of RIE process’ parameters in order to obtain a controllable process characterized by good selectivity and anisotropy. Presented in this study findings have shown that the SF₆ flow most significantly influence onto the RIE process’ results. Selected and optimized processing step will be used in the course of the fabrication of TFET devices, in future.

The paper presents a new computer program for calculating a combined standard uncertainty. It implements the algorithm described in JCGM 101:2008¹ which is concerned with the use of a Monte Carlo method as an implementation of the propagation of distributions for uncertainty evaluation. The accuracy of the calculation has been obtained by using the high quality random number generators. The paper describes the main principles of the program and compares the obtained result with example problems presented in JCGM Supplement 1.

We present the study of impact of the nanocrystal position and oxide layers thicknesses of the metal-insulatorsemiconductor structure with nanocrystals embedded in the insulator layer on the time-dependent current-voltage and capacitance-voltage characteristics. The theoretical considerations are based on the developed numerical model of a double-barrier MOS structure. The dominant current path in the structure is analysed in respect to the nanocrystals charging/discharging processes.

This paper presents an extended method of CMOS standard cells characterization for defect based voltage testing. It allows to estimate the probabilities of physical open defects occurrences in a cell, describes its faulty behavior caused by the defects and finds the test sequences that detect those faults. Finally, the minimal set of test sequences is selected to cover all detectable faults and the optimal complex test sequence is constructed. Experimental results for cells from industrial standard cell library are presented as well.

The aim of the work is to present a theoretical model of tunnel field effect transistor and to investigate the influence of the TFET’s construction parameters on the current-voltage characteristics. The solution to the problem of electrostatics in the structure is based on the numerical solution of two-dimensional Poisson equation and the electron and hole continuity equations. The tunneling process has been taken into account by a non-local interband generation model. Output and transfer characteristics of the double gate TFET were generated.

The purpose of the work is to find an appropriate flexible material to replace commonly used transparent conductive oxides (TCO) in photovoltaic (PV) emitter electrode applications. Authors show the alternative, potential possibility of using PEDOT conductive polymer as transparent emitter contacts for thin-film, flexible photovoltaic structures. The vast majority of contacts made of TCO layers, dominantly indium tin oxide ITO, are electrically unstable under the influence of mechanical stresses [1,2,3]. This drawback inhibits their usage in flexible devices, such as solar cells. The need of the development in the field of flexible PV structures induces searching for new materials. Investigated transparent conductive layers (TCL) were made of organic compositions based on PEDOT polymer and their parameters were compared with equally measured parameters of carbon nanotube (CNT) layers, commercial ITO and AgHT ultra-thin silver layers. Transparent conductive layers based on PEDOT:PSS compound were deposited on flexible substrates by screen printing technique. The analysis of achieved results shows the broad spectrum of application possibilities for PEDOT layers.

The results of investigations concerning anisotropic etching in 3M KOH and 25% TMAH solutions modified by tensioactive compounds such as alcohols, diols and a typical surfactant Triton X100 have been compared. Etching anisotropy was assessed on the basis of etch rates ratio V(110)/V(100). It was stated that the relation between surface tension of the solutions and etch rates of particular planes depend not only on the kind of surfactant but also on the kind of etching solution (KOH, TMAH). It points out an important role of TMA⁺ ions in the etching process, probably in the process of forming an adsorption layer, consisting of the molecules of tensioactive compounds on Si surface, which decides about etch rate. We have observed that this phenomenon occurs only at high concentration of TMA⁺ ions (25% TMAH). Reduction of TMAH concentration changes the properties of surfactant containing TMAH solutions. From all investigated solutions, the solutions that assured developing of (110) plane inclined at the angle of 45° to (100) substrate were selected. Such planes can be used as micromirrors in MOEMS structures. The solutions provide the etch rate ratio V(110)/V(100)<0.7, thus they were selected from hydroxide solutions containing surfactants. A simple way for etch rate anisotropy V(110)/V(100) assessment based on microscopic images etched structures has been proposed.

Today, methane sensors find applications mostly in safety alarm installations, gas parameters detection and air pollution classification. Such sensors and sensors elements exists for industry and home use. Under development area of methane sensors application is dedicated to ground gases monitoring. Proper monitoring of soil gases requires reliable and maintenance-free semi-constant and longtime examination at relatively low cost of equipment. The sensors for soil monitoring have to work on soil probe. Therefore, sensor is exposed to environment conditions, as a wide range of temperatures and a full scale of humidity changes, as well as rain, snow and wind, that are not specified for classical methane sensors. Development of such sensor is presented in this paper. The presented sensor construction consists of five commercial non dispersive infra-red (NDIR) methane sensing units, a set of temperature and humidity sensing units, a gas chamber equipped with a micro-fan, automated gas valves and also a microcontroller that controls the measuring procedure. The electronics part of sensor was installed into customized 3D printed housing equipped with self-developed gas valves. The main development of proposed sensor is on the side of experimental evaluation of construction reliability and results of data processing included safety procedures and function for hardware error correction. Redundant methane sensor units are used providing measurement error correction as well as improved measurement accuracy. The humidity and temperature sensors are used for internal compensation of methane measurements as well as for cutting-off the sensor from the environment when the conditions exceed allowable parameters. Results obtained during environment sensing prove that the gas concentration readings are not sensitive to gas chamber vertical or horizontal position. It is important as vertical sensor installation on soil probe is simpler that horizontal one. Data acquired during six month of environment monitoring prove that error correction of methane sensing units was essential for maintenance free sensor operation, despite used safety procedures.

A micro-cavity in-line Mach-Zehnder interferometer (μIMZI) is an optical sensing structure fabricated in an optical fiber. Its design allows for refractive index sensing of liquid and gas in picoliter volumes, making it suitable for biochemical and medical sensing where measured material is often scarce. The fabricated structures show satisfactory levels of sensitivity, from about 400 nm/RIU in the near-water range of solutions (n_D 1.336±0.003 RIU) to about 16 000 nm/RIU for solutions in approximate range from n_D = 1.35 RIU to n_D = 1.4 RIU. The structures were subjected to oxygen plasma, the process which was supposed to modify physical parameters of the structures, i.e., cavity surface wettability and roughness, and in consequence their sensitivity. As a result of the oxygen plasma modification we have observed a improved wettability of the structure surface, what makes it easier to introduce liquid into the cavity and simplifies the measurement process. In the case where the plasma processing is preceded by biological layer deposition, the bottom surface of the structure is smoothed and slightly deepened, causing a shift in the transmission spectrum and change in sensitivity.

In this work discuss an application of chemical method, i.e., Tollen’s reagent, for mirror fabrication on the end-face of the fiber with induced long-period grating (LPG). This simple and versatile technique can be used for thin silver layer deposition and formation of stable and well-reflecting mirrors for fiber-based devices. We have found that the LPGbased sensors working in reflective configuration at dispersion turning point (DTP) of higher order cladding modes allow for refractive index (RI) measurements with sensitivity reaching 4.429 nm/RIU. Such structures, after their proper biofunctionalization process, can be used as probes for label-free biosensing.

This paper discusses refractive index (n) measurement capabilities of micro-cavity with various diameters (d = 40, 54 and 60μm) fabricated in optical fibers by a femtosecond laser. The bottom of the cavity intersected the fiber’s core and the Mach-Zehnder interferometer effect was induced, allowing the measurement of the n of the liquid filling the cavity. After filling the cavity, a set of minima can be observed in fiber transmission spectrum which shift with change in n. Fabricated sensors exhibit high and linear sensitivity, which in the range of n=1.3333 to 1.3500 RIU barely depends on the cavity diameter in case of first observed minima. Next for different micro-cavity diameters the minima do not overlap in refractive index domain thus it is impossible to compare them in terms of the sensitivity. The highest sensitivity of up to more than 27 000 nm/RIU was obtained for the smallest cavity and the third observed minimum.

A luminescent lamp was constructed and tested. Phosphor excited by electrons is the source of light. The source of electrons is field emission cathode. The cathode is covered with nickel-carbon layer containing carbon nanotubes that enhance electron emission from the cathode. Results of luminance measurements are presented. Luminance is high enough for lighting application.

Critical current and current-voltage characteristics of epitaxial Nb(Ti)N submicron ultrathin structures were measured as function of temperature. For 700-nm-wide bridge we found current-driven vortex de-pinning at low temperatures and thermally activated flux flow closer to the transition temperature, as the limiting factors for the critical current density. For 100-nm-wide meander we observed combination of phase-slip activation and vortex-anti-vortex pair (VAP) thermal excitation. Our Nb(Ti)N meander structure demonstrates high de-pairing critical current densities ~10⁷ A/cm² at low temperatures, but the critical currents are much smaller due to presence of the local constrictions.

In this paper we present a concept of multi-line Microwave Photonic Filter (MPF) based on polarization beam splitting and polarization control in each line. Coefficients of investigated filter are determined by attenuation of its lines and that on the other hand can be manipulated by change of the polarization in the fiber. Presented results involve scattering parameters (S₂₁) measurements of optical path over polarization control unit rotation, scattering parameters (S₂₁) characteristics of investigated filter and transmission optimization capabilities.

The transmission properties of one dimensional PT-symmetric photonic crystal (PC) structure with gain and loss regions are presented. Obtained characteristics illustrate the influence of the structures parameters such as the ratio of the PC period to the operating wavelength, the number of the primitive cells creating PC, the loss and gain level (imaginary part of the refractive indices) on reflection and transmission coefficients. It demonstrates strong nonreciprocal response of the structure.

In this work, we report the technology of infrared photodetectors based on graphene layers (GLs). In the course of this work the new set of photolithography masks was especially designed to fabricate test structures. The new masks-set contains a matrix of different types of photodetector structures with varied active area dimensions, as well as additional module for characterization of electro-physical parameters of graphene and graphene-based devices. After careful optimization of consecutive technological steps, test structures were fabricated. First results of electrical characterization of obtained graphene-based photodetectors demonstrated that the developed technology was successful, however, further detailed optical characterization towards sensing parameters and potential applications in infrared detectors is necessary.

This paper reports the fabrication of n-type crystalline Si based solar cell using boron liquid solution (BLS) deposited by spray method for p-type emitter formation. The X-ray photoelectron spectroscopy (XPS) was used for the analysis of surface composition and electronic states of elements at the glass layer of dopant (GLD) obtained from BLS. The investigation of the borosilicate glass layer (BSG) created on a base of GLD during diffusion process were carried out by transmission electron microscopy (TEM). The diffusion profiles were determined by secondary ion mass spectrometry (SIMS) and electrochemical capacitance-voltage (EC-V) techniques, whereas the solar cells were characterized by the light current-voltage (I-V) and spectral measurements. The influence of a doping process on a minority carrier lifetime of the Si wafers was detected by quasi-steady-state photoconductance technique. Application of the elaborated BSL allowed to obtain the p-type Si emitters from BSG layer which exhibits unproblematic etching behaviour after diffusion process and final fabrication of the solar cells with the fill factor of 74% and photoconversion efficiency of 13.04 %. The elaborated BLS is a source which offers an attractive practicable alternative to form emitters on the n-type Si substrate.

In this paper, an impact of mounting of structures of nitride laser bars their performance, emitted optical power in particular, is presented. The laser bars of nitride edge-emitting lasers of ridge-waveguide type the InGaN/GaN active areas have been considered. Laser performance has been analysed with the aid of an advanced self-consistent thermalelectrical model, calibrated using experimental data for a single diode laser. The simulated laser bars emit at 408 nm. An optimal number of laser emitters and their various arrangments have been considered. An appliation of Cu heat sinks of various dimensions as well as the p-side-up or the p-side-down laser configurations have been analysed. Moreover a possible application of a diamond heat spreader has been also taken into account.

Using the orbital angular momentum of light for the development of a vortex interferometer, the underlying physics requires microwave/RF models,¹ as well as quantum mechanics for light^{1, 2} and fluid flow for semiconductor devices.^{3, 4} The combination of the aforementioned physical models yields simulations and results such as optical lattices,¹ or an Inverse Farday effect.⁵ The latter is explained as the absorption of optical angular momentum, generating extremely high instantenous magnetic fields due to radiation friction. An algorithmic reduction across the computational methods used in microwaves, lasers, quantum optics and holography is performed in order to explain electromagnetic field interactions in a single computational framework. This work presents a computational model for photon-electron interactions, being a simplified gauge theory described using differentials or disturbances (photons) instead of integrals or fields. The model is based on treating the Z-axis variables as a Laplace fluid with spatial harmonics, and the XY plane as Maxwell's equations on boundaries. The result is a unified, coherent, graphical computational method of describing the photon qualitatively, quantitatively and with proportion. The model relies on five variables and is described using two equations, which use emitted power, cavity wavelength, input frequency, phase and time. Phase is treated as a rotated physical dimension under gauge theory of Feynmann's QED. In essence, this model allows the electromagnetic field to be treated with it's specific crystallography. The model itself is described in Python programming language.

PACS 42.50.Pq, 31.30.J-, 03.70.+k, 11.10.-z, 67.10.Hk

In this paper a concept of a new bulk structure of p⁺-υ-n⁺ silicon photodiodes optimized for the detection of fast-changing radiation at the 1064 nm wavelength is presented. The design and technology for two types of quadrant photodiodes, the 8-segment photodiode and the 32-element linear photodiode array that were developed according to the concept are described.

Electric and photoelectric parameters of the photodiodes mentioned above are presented.

In this paper, the design and technology of two types of 16-element photodiode arrays is described. The arrays were developed by the ITE and are to be used in detection of microdeflection of laser radiation at the Institute of Metrology and Biomedical Engineering in the Faculty of Mechatronics of Warsaw University of Technology.

The electrical and photoelectrical parameters of the arrays are presented.

The paper presents test and inspection strategies used in the company Fideltronik Poland, Sucha Beskidzka during the process of assembly of advanced electronic systems. As the example, the manufacturing process of modules for controlling and configuration of charts for video transmission has been analyzed. Various diagnostic methods such as Solder Paste Inspection (SPI), Automated Optical Inspection (AOI), Automated X-ray Inspection AXI and Functional Circuit Test FCT have been used to detect failures at different manufacturing stages of the modules and various repair actions have been proposed .

This paper presents investigation results obtained with the measuring system enabling detection of acetone with concentrations lower than 1 ppm. In the experiment we used both conventional preconcentrators made from materials such as stainless steel and quartz tubes and a micropreconcentrator manufactured in MEMS technology. The active volume of all preconcentrators was equal to enable comparisons of their performance. As a gas detector at the output of the measurement system we used both commercial semiconductor gas sensor and a mass spectrometer for comparison purposes. The obtained results show that the measurement system with micropreconcentrator and a commercial gas sensor can be used for detection of low level acetone present in the air exhaled by diabetics.

A test chip for investigation of junctionless FETs as sub-THz electromagnetic radiation detectors is presented. A number of sensors have been included in the chip designed for production on the SOI substrate. The sensors differ one from one another by the presence of an antenna, transistor layout and doping details. A technology for fabrication of transistors with the self-aligned gate and well-controlled gate to n⁺ source/drain separation distance has been developed. Results of device simulation and electrical characterization are presented in the paper.

The measurement system for laboratory array of gas sensors was constructed. The system can be used to measure the response characteristic of resistive metal oxide (MO_x) gas sensors. Proposed system is flexible and reconfigurable easy, to perform high and low resistivity measurements.

Results of fabrication as well as electrical and stability characterization of thick-film high ohmic resistors are described in this paper. Five commercially available resistive compositions with sheet resistance of 1, 10, and 100 MΩ/sq were applied. The best properties were obtained for the lowest sheet resistance pastes, for which voltage coefficient of resistance (VCR) was lower than 3 ppm/V and hot temperature coefficient of resistance (HTCR) below 50 ppm/°C. Effect of resistor length on sheet resistance and impact of termination material were analyzed. High voltage pulse stress at 2 kV had negligible influence on resistors’ properties.

Glass and fiber structures with Indium Tin Oxide (ITO) coating were subjected to annealing in order to identify impact of the thermal treatment on their optical and electrochemical properties. It is shown that the annealing process significantly modifies optical properties and thickness of the films, which are crucial for performance of optical fiber sensors. Moreover, it visibly improves electrochemical activity of ITO on glass slides and thicker (∅=400 μm) ITO-coated fibers, whereas in the case of thinner fibers (∅=125 μm) it could lead to a loss of their electrochemical activity. Depending on the applied substrate and the annealing process, the investigated structures with ITO coating can be further used as fiber-based sensors with integrated opto-electrochemical readout.

The aim of the study was to elucidate influence parameters of magnetron sputtering process on growth rate and quality of titanium dioxide thin films. TiO₂ films were produced on two inch silicon wafers by means of magnetron sputtering method. Characterization of samples was performed using ellipsometer and atomic force microscope (AFM). Currentvoltage (I-V) and capacitance-voltage (C-V) measurements were also carried out. The results enable to determine impact of pressure, power, gases flow and process duration on the physical parameters obtained layers such as electrical permittivity, flat band voltage and surface topography. Experiments were designed according to orthogonal array Taguchi method. Respective trends impact were plotted.

This work presents theoretical and experimental results of antireflective coatings (ARCs) obtained for applications in silicon solar cells. ARCs were derived from sol-gel process and dip-coated using silica (SiO₂) and titania (TiO₂). Theoretical results were obtained using 2×2 transfer matrix calculation method. Technological process of SiO₂ and TiO₂ thin film fabrication as well as measurement techniques are described in this paper. Strong correlation between theoretical and experimental data is demonstrated. It is shown, that weighted average reflection from a substrate can be reduced ten times with the use of SiO₂/TiO₂/Si double layer ARCs, when compared to a bare silica substrate.

Epitaxial lift-off (ELO) is a process which enables the removal of solar cell structures (one junction GaAs, two junction GaAs/InGaP or three junction GaAs/InGaAs/InGaP) from the substrate on which they are grown and their transfer onto lightweight carriers such as metal or polymeric insulator films. The said solar cells exhibit superior power conversion efficiency compared with alternative single-junction photovoltaic cell designs such as those based on crystalline Si, copper indium gallium sulfide (CIGS) or CdTe. The major advantage of ELO solar cells is the potential for wafer reuse, which can enable significant manufacturing cost reduction by minimizing the consumption of expensive wafers. Here in this work we have grown one junction GaAs solar cells on GaAs (100) substrates. A 10 nm thick AlAs layer has been used as a release layer, which has been selectively etched in HF solution. We have investigated different methods of transferring thin films onto polymer and copper foils, including the usage of temporary mounting adhesives and electro-conductive pastes. Lift-off has been demonstrated to be a very promising technique for producing affordable solar cells with a very high efficiency of up to 30%.

Recently photovoltaics attracts much attention of research and industry. The multidirectional studies are carried out in order to improve solar cells performance, the innovative materials are still searched and existing materials and technology are optimized. In the multilayer structure of CIGS solar cells molybdenum (Mo) layer is used as a back contact. Mo layers meet all requirements for back side electrode: low resistivity, good adhesion to the substrate, high optical reflection in the visible range, columnar structure for Na ions diffusion, formation of an ohmic contact with the ptype CIGS absorber layer, and high stability during the corrosive selenization process. The high adhesion to the substrate and low resistivity in single Mo layer is difficult to be achieved because both properties depend on the deposition parameters, particularly on working gas pressure. Therefore Mo bilayers are applied as a back contact for CIGS solar cells. In this work the Mo layers were deposited by medium frequency sputtering at different process parameters. The effect of substrate temperature within the range of 50°C-200°C and working gas pressure from 0.7 mTorr to 7 mTorr on crystalline structure of Mo layers was studied.

In this work, we present the design of the technology and fabrication of TFTs with amorphous IGZO semiconductor and high-k gate dielectric layer in the form of hafnium oxide (HfO_x). In the course of this work, the IGZO fabrication was optimized by means of Taguchi orthogonal tables approach in order to obtain an active semiconductor with reasonable high concentration of charge carriers, low roughness and relatively high mobility. The obtained Thin-Film Transistors can be characterized by very good electrical parameters, i.e., the effective mobility (μ_eff ≈ 12.8 cm²V^-1s^-1) significantly higher than that for a-Si TFTs (μ_eff ≈ 1 cm²V^-1s^-1). However, the value of sub-threshold swing (i.e., 640 mV/dec) points that the interfacial properties of IGZO/HfO_x stack is characterized by high value of interface states density (D_it) which, in turn, demands further optimization for future applications of the demonstrated TFT structures.

In this paper, the results of the initial work on determining the photoelectric properties of graphene detector operating in a photoconductive mode are presented. Graphene is considered as a material for uncooled fast detectors. The investigation has been done by electrical and optical characterization. Two values of substrate resistivity have been used in the project – below 1 Ωcm and higher than 1.6 kΩcm. Measurements of detectors response to short, strong light pulses were conducted. Presented studies show that the use of high resistivity substrates is necessary to prevent capacitive shorting of the signal to the substrate, causing signal losses and increasing response time.

Amorphous a-SiC_xN_y:H thin films may be an alternative to a-Si:N:H coatings which are commonly used in silicon solar cells. This material was obtained by PECVD (13.56 MHz) method. The reaction gases used: silane, methane, nitrogen and ammonia. The structure of the layers were investigated by scanning electron microscopy (SEM) and infrared spectroscopy (FTIR). IR absorption spectra of a-SiC_xN_y:H layers confirmed the presence of various hydrogen bonds – it is important for passivation of Si structural defects. The ellipsometric measurements were implemented to determine the thickness of layers d, refractive index n, extinction coefficient k and energy gap E_g. The values of the energy gap of a-SiC_xN_y:H layers are in the range from 1.89 to 4.34 eV. The correlation between energy gap of materials and refractive index was found. Generally the introduction of N and/or C into the amorphous silicon network rapidly increases the E_g values.