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The chaotic behaviours in the p-Ge photoconductor system are studied by changing the photo-excitation coefficient and the routes and parameter conditions are given for chaos generation in this system. A scheme for controlling chaos in the p-Ge photoconductor is presented by adding an ac bias current. Numerical simulations show that this scheme can be effectively used to control chaotic states into stable period states for this system. Moreover, the different period states with different period numbers can be obtained by appropriately adjusting the amplitude, frequency, and initial phase of the additional ac current. [ABSTRACT FROM AUTHOR]

Typical spectra of the noise power density of uncooled photoresistors manufactured according to different industrial technologies are presented. It is shown that 1/F-type noise is responsible for the principal contribution to the spectrum. [ABSTRACT FROM AUTHOR]

A laser beam induced current (LBIC) map of a photoactive surface is a very useful tool when it is necessary to study the spatial variability of properties such as photoconverter efficiency or factors connected with the recombination of carriers. Obtaining high spatial resolution LBIC maps involves irradiating the photoactive surface with a photonic beam with Gaussian power distribution and with a low dispersion coefficient. Laser emission fulfils these characteristics, but against it is the fact that it is highly monochromatic and therefore has a spectral distribution different to solar emissions. This work presents an instrumental system and procedure to obtain high spatial resolution LBIC maps in conditions approximating solar irradiation. The methodology developed consists of a trichromatic irradiation system based on three sources of laser excitation with emission in the red, green, and blue zones of the electromagnetic spectrum. The relative irradiation powers are determined by either solar spectrum distribution or Planck’s emission formula which provides information approximate to the behavior of the system if it were under solar irradiation. In turn, an algorithm and a procedure have been developed to be able to form images based on the scans performed by the three lasers, providing information about the photoconverter efficiency of photovoltaic devices under the irradiation conditions used. This system has been checked with three photosensitive devices based on three different technologies: a commercial silicon photodiode, a commercial photoresistor, and a dye-sensitized solar cell. These devices make it possible to check how the superficial quantum efficiency has areas dependent upon the excitation wavelength while it has been possible to measure global incident photon-to-current efficiency values approximating those that would be obtained under irradiation conditions with sunlight. [ABSTRACT FROM AUTHOR]

A novel plastic packaging of a piezoresistive pressure sensor using a patterned ultra-thick photoresist is experimentally and theoretically investigated. Two pressure sensor packages of the sacrifice-replacement and dam-ring type were used in this study. The characteristics of the packaged pressure sensors were investigated by using a finiteelement (FE) model and experimental measurements. The results show that the thermal signal drift of the packaged pressure sensor with a small sensing-channel opening or with a thin silicon membrane for the dam-ring approach had a high packaging induced thermal stress, leading to a high temperature coefficient of span (TCO) response of -0.19% span/°C. The results also show that the thermal signal drift of the packaged pressure sensors with a large sensing-channel opening for sacrifice-replacement approach significantly reduced packaging induced thermal stress, and hence a low TCO response of -0.065% span/°C. However, the packaged pressure sensors of both the sacrifice-replacement and dam-ring type still met the specification -0.2% span/°C of the unpackaged pressure sensor. In addition, the size of proposed packages was 4 × 4 × 1.5 mm3 which was about seven times less than the commercialized packages. With the same packaging requirement, the proposed packaging approaches may provide an adequate solution for use in other opencavity sensors, such as gas sensors, image sensors, and humidity sensors. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we prepared a silicon-containing polymer nanosheet, poly(neo-pentylmethacrylamide-co-4-(trimethylsilyl)phenyl)methacrylamide (p(nPMA/SiPhMA)), for positive-tone photoresist application. p(nPMA/SiPhMA) forms a stable monolayer at the air–water interface and the polymer monolayer can be transferred onto a solid substrate using the Langmuir–Blodgett technique, when the SiPhMA molar contents are below 38%. Sixty layers of p(nPMA/SiPhMA) nanosheet were deposited onto a silicon substrate and deep UV was irradiated through a photomask to the deposited film. After development of the irradiated film with alkaline solution, a positive-tone fine pattern with a 0.75μm resolution, which is the highest resolution of the photomask, was clearly drawn. UV–vis and FT-IR spectroscopy indicates the formation of alkaline soluble groups, such as C#x2013;O–Si after photodecomposition. Moreover, p(nPMA/PhSiMA) polymer nanosheet shows three times higher oxygen etching resistance compared to poly(methylmethacrylate) (PMMA). The high plasma resistance of the polymer nanosheet film is caused by not only the presence of Si atom in the film but also a closely packed and high molecular orientated structure of the polymer nanosheets. [Copyright &y& Elsevier]

Abstract: Rats sweep their vibrissae in a rhythmic and coordinated fashion in order to acquire tactile information from their environment. Measuring vibrissae movement has become a matter of increased attention, from several labs, over the last few years. We describe the design and construction of an inexpensive photoresistive sensor that registers horizontal vibrissae movement. The device consists of an LED array and a light-dependent resistor (LDR) covered by a coating with varying transparency along its axis. When a vibrissa is located in the sensor, it generates a shadowy line over the photosensitive material, thus changing the LDR resistance. These changes are transduced into voltage changes. Our measurements on vibrissa show that this simple and inexpensive sensor effectively monitors the movement of a single vibrissa. [Copyright &y& Elsevier]

Abstract: Light depended resistors (LDR) or photoresistors are semiconductor devices that are changing resistance under illumination. These devices have many applications in industrial controls: item counters, presence and proximity sensors, flame detectors, photometric devices, etc. If the light falling on the device has energy which is greater than the bandgap of the semiconductor, photons absorbed by the semiconductor excite electron–hole pairs which result in lowering the resistance of the semiconductor. Generally, these devices are made of semiconductors such as CdS or CdSe using a thin film technology, since they have traps and misfits in their atomic structure, leading to high dark current and noise. In this work, we describe a novel approach for a novel family of high sensitive light detectors made of single-crystalline silicon. Basic sensor was built in a flat shape providing lateral electrical transport of excited charged carriers. Simple laboratory methods were used to diffuse impurities on both sides of the sensor. The sample shows high sensitivity due to light intensity variation from dark to strong light (∼96,000lx). A 30 times variation in the sample resistance was obtained. [Copyright &y& Elsevier]

• A single-step solvothermal method is used to synthesize CuS and Cu 9 S 5 micro-flowers. • Hexagonal CuS and Rhombohedral Cu 9 S 5 are refined using FULLPROF suit program. • Higher surface area and efficient light-trapping enhance the photoconduction in micro-flowers. • ~110 times increase in the photocurrent is observed for Cu 9 S 5 than CuS. • Cu 9 S 5 attained 2.5 × 10−4 A/W Responsivity and 2.3 × 1010 Jones Detectivity at 980 nm. [Display omitted] Owing to the alteration in the fundamental properties even by a slight variation in Cu/S ratio, the Cu–S system has been complicated and its role in photoconductive devices has been rarely investigated. Herein, CuS and Cu 9 S 5 micro-flowers have been synthesized via a single-step solvothermal process and their photoconductors have been fabricated to unveil the optoelectronic characteristics. By increasing a Cu/S ratio from CuS to Cu 9 S 5 , the reduction in bandgap from 1.60 to 1.09 eV has been observed. In addition, the impact of bandgap on conductivity under dark and light has been investigated. Under Halogen light exposure, ~110 times increase in the photocurrent for Cu 9 S 5 has been observed than CuS. The detectivity and responsivity of CuS and Cu 9 S 5 were obtained to be 9.26 × 105, 6.1 × 106 Jones and 1.37 × 10−8, 1 × 10−6 A/W under Halogen light. In addition, the Cu 9 S 5 photoconductor attained maximum responsivity, 2.5 × 10−4 A/W, and detectivity, 2.3 × 1010 Jones at 980 nm. More importantly, the photoconduction mechanism for CuS and Cu 9 S 5 has been studied in-depth and the role of the Cu/S ratio on the photoconductivity has been evaluated. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present a method that simplifies the interconnect complexity of N × M resistive sensor arrays from N × M to N + M. In this method, we propose to use two sets of interconnection lines in row–column fashion with all the sensor elements having one of their ends connected to a row line and other end to a column line. This interconnection overloading results in crosstalk among all the elements. This crosstalk causes the spreading of information over the whole array. The proposed circuit in this method takes care of this effect by minimizing the crosstalk. The circuit makes use of the concept of virtual same potential at the inputs of an operational amplifier in negative feedback to obtain a sufficient isolation among various elements. We theoretically present the suitability of the method for small/moderate sized sensor arrays and experimentally verify the predicted behavior by lock-in-amplifier based measurements on a light dependent resistor (LDR) in a 4×4 resistor array. Finally, we present a successful implementation of this method on a 16×16 imaging array of LDR. [Copyright &y& Elsevier]

In this brief communication, we introduce a Chua's circuit based on a photoresistor nonlinear device and experimentally investigate the effects of controlling it by a light source. Light control affects the dynamics of the circuit in several ways, and the circuit can be controlled to exhibit periodicity, period-doubling bifurcations and chaotic attractors. The dynamics of the circuit that operates at frequencies up to kilohertz is strongly influenced by using periodic driving signals at low frequencies. In particular, experimental results have shown that an unstable intermittent behavior can be observed and that this can be stabilized by using feedback. Synchronization of two circuits has also been investigated. [ABSTRACT FROM AUTHOR]

Abstract: We present N-(p-anilinesulfonyloxy)-1,8-naphthalimide (ASNI) as fluorescence imaging material based on a novel fluorescence imaging mechanism. ASNI is composed of two functional moieties in one molecule: an acid-reactive fluorescence probe and a photoacid generator (PAG). When ASNI is photoirradiated, a bond in the PAG moiety breaks and an acid is generated. The fluorescence probe moiety then detects the acid and fluoresces. We call this novel mechanism a self-contained photoreaction (SCP). The photophysical properties and photoreactivity of ASNI were measured and compared with those of a prototype PAG, N-(phenylsulfonyloxy)-1,8-naphthalimide. These were well represented by density functional theory calculations. SCP permits one-step fluorescence imaging without any wet or dry developing process. [Copyright &y& Elsevier]

The application of a Shack-Hartmann sensor with holographic lenslet array to the measurements of wavefront aberrations in a speckle field is offered. The main feature of the method is that the tested wave front can be compared with an arbitrary wavefront preliminary recorded in the holographic memory of the array. An iterative algorithm of the sensor work for measuring the variable speckled wavefronts is offered. The experimental results of measurements of the curvature of a spherical speckled wave are presented. The possibility to use the method proposed in the analysis of deformations of a rough surface is shown. [ABSTRACT FROM AUTHOR]

Mono- and multilayers of nitroazobenzene (NAB), azobenzene (AD), nitrobiphenyl (NBP), biphenyl (BP), and fluorene (FL) were covalently bonded to flat pyrolyzed photoresist films (PPF) by electrochemical reduction of their diazonium derivatives. The structure and orientation of the molecular layers were probed with ATR-FT-IR and Raman spectroscopy. A hemispherical germanium ATR element used with p-polarized light at 65° incidence angle yielded high signal/noise IR spectra for monolayer coverage of molecules on PPF. The IR spectra are dominated by in-plane vibrational modes in the 1000-2000-cm-1 spectral range but also exhibit weaker out-of-plane deformations in the 650-1000-cm-1 region. The average tilt angle with respect to the surface normal for the various molecules varied from 31.0 ± 4.5° for NAB to 44.2 ± 54° for FL with AD, NBP, and BP exhibiting intermediate adsorption geometries. Raman intensity ratios of NAB and AD for p- and s-polarized incident light support the conclusion that the chemisorbed molecules are in a predominantly upright orientation. The results unequivocally indicate that molecules electroreduced from their diazonium precursors are not chemisorbed flat on the PPF surface, but rather at an angle, similar to the behavior of Au/thiol self-assembled monolayers, Langmuir-Blodgett films, and porphyrin molecules chemisorbed thermally on silicon and PPF from alkyne and alkene precursors. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we present new results achieved with a sputtered multilayer system consisting of In x O y N z and gold-nano-dots. This system shows not only electrical but also optical gas sensitivity. The optical sensing effect is enhanced by the gold-nano-dots which are randomly distributed on and inside each In x O y N z layer. The optical measuring system consists of a tuneable light source (or alternatively of a simple light emitting diode) and a CdS-photoresistor. As an example of the optical gas sensing effect we show the sensitivity to hydrogen at a temperature of 400°C. [Copyright &y& Elsevier]

PbSe is a IV–VI compound semiconductor with a narrow band gap (0.26 eV), used in photodetectors, photoresistors and photoemitters in the infrared (IR). This paper reports the first instance of PbSe formation by electrochemical atomic layer epitaxy (EC-ALE). The film’s composition and structure were characterized using electron probe microanalysis (EPMA) and X-ray diffraction (XRD), respectively. The optical properties were studied via infrared absorption measurements. Films were stoichiometric via EPMA, a Pb/Se ratio of one. XRD indicated the expected rock salt structure for PbSe, and a preferred (2 0 0) orientation. IR adsorption studies, of films grown with 10–50 cycles, showed strong blue shifts of the fundamental absorption edge, which was believed to result from quantum confinement in the thin films. [Copyright &y& Elsevier]

This paper describes a simple batch process for fabrication of microlens and microlens array at the end of an optical fiber or an optical fiber bundle using self-photolithography and etching techniques. A photoresist micro-cylinder was exactly formed at the core of the fiber end by exposing an UV light from the other and of the fiber and conventional development, rinse processes. A photoresist microlens was formed by thermal reflowing of the fiber at 170°C for 1 h. A measurement of transmissivity showed that the fabricated photoresist microlens is applicable for a wavelength that is longer than 450nm. Alternatively, a glass microlens was fabricated at the core of the fiber by dry etching with an SF[SUB6] gas using the photoresist microlens as a mask. The focusing of the lensed fiber was confirmed and simulation work showed that the lensed fiber could focus the light with a beam spot of 2 μm, numerical aperure (NA) of 0.285 and a depth of focus of 16 μm. [ABSTRACT FROM AUTHOR]

An organic SOG, the Hybird-Organic-Siloxane-Polymer (HOSP), has high applicability to ULSI processes, because of the low dielectric constant of about 2.5. However, the HOSP film will be damaged after photoresist removal. The function groups of HOSP will be destroyed by O2 plasma ashing and chemical wet stripper, which leads to electrical degradation. In order to avoid the issue, H2 plasma treatment is proposed to prevent HOSP film from photoresisit stripping damage. It is found that leakage current is decreased significantly and the dielectric constant is still maintained at a low k value even after photoresist stripping. Therefore, H2 plasma treatment is an effective technique to enhance the resistance of HOSP film against photoresist stripping damage. [Copyright &y& Elsevier]

Describes an experimental investigation of millimeter-wave oscillators employing a single and InGaAs/InP heterojunction bipolar photo-resistors (photo-HBTs). Information on the photo-HBT self-oscillator; Evaluation of analog modulation and digital modulation; Advantages of the millimeter-wave oscillators.

It is demonstrated that variband near-surface layers with even a small composition gradient can provide ultimate photomodulation (corresponding to the absence of the surface recombination) of the conductivity of thin CdHgTe samples used for manufacturing threshold photoresistors (including those of the SPRITE type) for the wavelengths λ = 8-12 µm and λ = 3-5 µm. This is explained by the formation (even in weak variband layers) of a special profile of the photoexcited carrier distribution that inhibits their diffusion to the surface. As is known, the introduction of the near-surface variband layers with a small composition gradient must not lead to any substantial increase in the number of defects in the sample. [ABSTRACT FROM AUTHOR]

The resolution of a chemically amplified resist tends to be degraded due to postexposure delay (PED). To elucidate the characteristics of the degradation, we conducted studies employing simulations of lithographic processes. In performing such studies, simulation parameters (diffusion length of the photoactive compound, surface inhibition parameters) are normally estimated by calculating the distribution of the photoactive compound concentration in the resist film using Dill's ABC parameters for a conventional resist. However, bleaching in many chemically amplified resists does not occur (parameter A = 0), making it difficult to compute the ABC parameters. Therefore, we studied a method of estimating simulation parameters that uses the accumulated exposure energy instead of the concentration distribution of the photoactive compound in the resist film. Simulation parameters were estimated for a t-BOC chemically amplified resist for use with KrF excimer lasers. The values obtained were input to the PROLITH/2 photoresist profile simulator, and profiles were calculated. Pattern calculations assumed a wavelength of 248 nm, with NA = 0.5 and a coherence factor of 0.6, and line and space of 0.25 μm and 0.30 μm. The results were compared with SEM observations to confirm the validity of the method of estimation. Good agreement was found between the simulated results and the SEM observations, confirming the soundness of the estimation method. In addition, simulations confirmed that the cause of resolution deterioration, as PED progresses, is the formation of a surface-inhibiting layer extending deep into the resist film. © 1999 Scripta Technica, Electron Comm Jpn Pt 2, 82(2): 30–38, 1999 [ABSTRACT FROM AUTHOR]

A theory is developed for photoresistors made up of trapezoidal δ-doped superlattices and their sensitivity to long-wavelength infrared light, based on a model proposed previously by the authors. It is shown that despite interband absorption of the infrared light and photogeneration of electron-hole pairs, the photoconductivity of the superlattice is unipolar, and that the photoelectric gain and photosensitivity of a photoresistor incorporating such a superlattice can reach enormous values. It is established that the lifetime of electrons and holes, determined by tunnel-radiative transitions, determines the kinetics of the photoconductivity decay. A paradoxical effect is predicted: the voltage photosensitivity of a trapezoidal superlattice, in contrast to all other types of photoresistors, is nearly independent of the lifetime of the photocarriers and level of doping (i.e., concentration of equilibrium carriers), and can have a gigantic value. The spectral sensitivity R(ω) is calculated, and it is shown that near the absorption edge R(ω) increases linearly with increasing photon energy. The spectral density of generation-recombination noise is found, along with the detectivity of such photoresistors. It is noted that this type of photoresistor allows fast erasure of the photoconductivity. [ABSTRACT FROM AUTHOR]

An inexpensive technique is described for measuring eyelid closure during classical (Pavlovian) conditioning experiments. This technique employs a Coulbourn Instruments Co. densitometric device that focuses a beam of infrared light on the cornea. Reflection of the light is interrupted by the eyelids when they are closed, which is sensed by an infrared detector. The latter causes a voltage change to occur, which can then be measured in a variety of ways. Details of both the hardware required and software developed for this purpose are described. [ABSTRACT FROM AUTHOR]

Recently, there has been an increased need for highly sensitive solid-state imaging devices to develop high-resolution and high-speed image sensors. Crystalline selenium is a suitable material for a photosensitive layer because of its high absorption coefficient in the visible light region. In our experiment with an image pick-up tube using crystalline selenium as a photosensitive layer, a high-resolution image was obtained for the first time. In addition, test sandwich cells have been fabricated to demonstrate a large photocurrent multiplication phenomenon with very high quantum efficiency greatly exceeding unity as a result of injection carriers from an external electrode caused by a high electric field at the interface between the crystalline selenium and the metal electrode. [ABSTRACT FROM AUTHOR]

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Abstract: In this study, the feasibility of using a photoconductor with a Ga2O3/CuGaSe2 heterojunction for visible light sensors was investigated. We propose a hole-blocking structure using gallium oxide (Ga2O3) for CuIn1−xGaxSe1−ySy (CIGS) thin film to reduce dark current. Experimental results showed that this structure drastically reduced the dark current. Then, avalanche multiplication phenomenon was observed at an applied voltage of over 6V. However, this structure had sensitivity only in the ultraviolet light region. It seemed the depletion region in the heterojunction spread almost completely in the Ga2O3 layer but not in the CIGS layer because the carrier density of the non-doped Ga2O3 layer was much lower than that of the CIGS layer. We therefore used tin-doped Ga2O3 (Ga2O3:Sn) for the n-type layer to increase carrier density. As a result, the depletion region shifted to the CIGS film and the cells had sensitivity in all visible regions. These results indicate that the Ga2O3:Sn/CuGaSe2 heterojunction is feasible for visible light photoconductors. [Copyright &y& Elsevier]

This paper describes a four-quadrant analogue divider making use of photoresistors as voltage-controlled resistances. The range of operation is between -l0 and + 10 volts and the accuracy is within 5% over the useful range.
Analogue division is normally performed by making use of multipliers in a feedback system. Such circuits becomes unstable when the divisor approaches zero. Because of this difficulty, division is normally avoided. However, sometimes ratio of analogue signals are required and one or both may pass through zero. [ABSTRACT FROM AUTHOR]

This letter presents the fabrication of 340-GHz copper folded waveguides (FWGs) using the UV-LIGA method. During the process, KMPR photoresist was employed instead of SU-8 due to its easy removability after electroforming. KMPR patterns with a sidewall height of 300 \mu\m and a trench width of 100 \mu\m were achieved repeatedly under one single-spin deposition and optimized processing conditions, such as UV exposure dose and KMPR bake temperature and time. The dimensional accuracies of the wide side (500 \mu\m) and narrow side (100 \mu\m) of the copper FWGs were found to be \leqslant \6 and \leqslant \2\ \mu\m, respectively, and the sidewall surface roughness was about 44 nm, with a profile of about 90^\circ. [ABSTRACT FROM PUBLISHER]

Abstract: Ultraviolet photoresistors based on ZnO thin films were fabricated on sapphire substrates with MgO buffer layer by plasma-assisted molecular beam epitaxy. An extremely large dark resistance up to 4×1010 Ω was obtained and the dark/photo resistance ratio is up to 2.3×105 with a light intensity of 1.3mW/cm2 at 370nm. The spectral response shows a large responsivity of more than 1Ω−1 W−1 in the UV region. The photo-resistance depends linearly on the reciprocal of the optical power density for more than two orders of magnitude. The transient response property shows a decay time of 167μs and the relaxation mechanisms are also discussed. [Copyright &y& Elsevier]

A comparative study of n-MgZnO/p-Si UV-B photodetector performance was carried out with different device structures. The experimental results demonstrate superior photoresponse characteristics of the p-n heterojunction detector against the Schottky type metal-semiconductor-metal counterpart, including a sharper cutoff wavelength at 300 nm, a larger peak photoresponsivity of 1 A/W, and a faster response speed. The role of built-in field and low interface scattering in p-n heterojunction is explored, and the energy band diagram of n-MgZnO/p-Si is employed to interpret the efficient suppression of visible light photoresponse from Si substrate, revealing the applicability of this heterostructure in fabrication of deep ultraviolet detectors. [ABSTRACT FROM AUTHOR]

A low-cost mechanical exfoliation method is presented to transfer graphite to graphene for free-standing beam arrays. Nickel film or photoresist is used to peel off and transfer patterned single-layer or multilayer graphene onto substrates with macroscopic continuity. Free-standing graphene beam arrays are fabricated on both silicon and polymer substrates. Their mechanical properties are studied by atomic force microscopy. Finally, a graphene based radio frequency switch is demonstrated, with its pull-in voltage and graphene-silicon junction investigated. [ABSTRACT FROM AUTHOR]

Results of photoresponse measurements performed on long-wave infrared photoconductors fabricated from HgTe-HgCdTe superlattices grown by molecular beam epitaxy are presented. Absolute spectral photoresponse measurements as a function of temperature and applied electric field have be undertaken, with the peak photoresponse of 3.3×103 V/W measured at 100 K. Sweepout effects were observed for fields greater than 20 V/cm and quantum efficiencies approaching 80% for 5 μm thick devices have been predicted from absorption measurements of grown material. [ABSTRACT FROM AUTHOR]

Plasmonic enhancement of a quantum dot infrared photodetector (QDIP) integrated with a metal photonic crystal (MPC) depends on the direction of the incident light, air-side versus substrate-side illumination. Compared with air-side illumination, substrate-side illumination on the same photodetector results in more than 2× enhancement in detectivity. This is explained by more efficient excitation of surface plasma waves (SPWs) at the MPC/QDIP interface in the back-side geometry. The air/MPC/semiconductor structure is optically asymmetric and has different SPW coupling leading to higher photoresponse for substrate-side illumination. This agrees with simulation and provides direct evidence that the detectivity enhancement is due to the coupling to SPWs and is crucially affected by light incident direction. [ABSTRACT FROM AUTHOR]

The functional properties of a photoresistor biased by ac voltage have been studied. A method for the Fourier analysis of the photoconductivity kinetics using ac voltage applied to the photoresistor is proposed. It is shown that the response of a photoresistor is proportional to the product of an electric bias signal and an intensity-modulated optical signal. [ABSTRACT FROM AUTHOR]

The results of studies of the spectral characteristics of the m-n°-n-structure with a base area on the basis of thin epitaxial specified undoped GaInAs and oxygendoped AlGaAs layers are presented. It is experimentally revealed that own defects and oxygen impurities introduced into the thin active n-area, whose thickness is about the diffusion length, promote the greater photoresponse in the impurity spectral band (1.2 and 1.55 μm). At the same time, impurities present in GaInAs at the background level can be excited, although ineffectively, from the quasineutral part of the active region depleted by the blocking voltage. [ABSTRACT FROM AUTHOR]

The Van der Waals (vdWs) hetero-structures consist of two-dimensional materials have received extensive attention, which is due to its attractive electrical and optoelectronic properties. In this paper, the high-quality large-size graphene film was first prepared by the chemical vapor deposition (CVD) method; then, graphene film was transferred to SiO2/Si substrate; next, the graphene/WS2 and graphene/MoS2 hetero-structures were prepared by the atmospheric pressure chemical vapor deposition method, which can be achieved by directly growing WS2 and MoS2 material on graphene/SiO2/Si substrate. Finally, the test characterization of graphene/TMDs hetero-structures was performed by AFM, SEM, EDX, Raman and PL spectroscopy to obtain and grasp the morphology and luminescence laws. The test results show that graphene/TMDs vdWs hetero-structures have the very excellent film quality and spectral characteristics. There is the built-in electric field at the interface of graphene/TMDs heterojunction, which can lead to the effective separation of photo-generated electron–hole pairs. Monolayer WS2 and MoS2 material have the strong broadband absorption capabilities, the photo-generated electrons from WS2 can transfer to the underlying p-type graphene when graphene/WS2 hetero-structures material is exposed to the light, and the remaining holes can induced the light gate effect, which is contrast to the ordinary semiconductor photoconductors. The research on spectral characteristics of graphene/TMDs hetero-structures can pave the way for the application of novel optoelectronic devices. [ABSTRACT FROM AUTHOR]

Polycrystalline Lead Oxide (poly-PbO) was considered one of the most promising photoconductors for the direct conversion X-ray medical imaging detectors due to its previous success in optical imaging, i.e., as an optical target in so-called Plumbicon video pick-up tubes. However, a signal lag which accompanies X-ray excitation, makes poly-PbO inapplicable as an X-ray-to-charge transducer in real-time X-ray imaging. In contrast, the recently synthesized Amorphous Lead Oxide (a-PbO) photoconductor is essentially lag-free. Here, we report on our approach to a PbO detector where a thin layer of a-PbO is combined with a thick layer of poly-PbO for lag-free operation. In the presented a-PbO/poly-PbO bilayer structure, the poly-PbO layer serves as an X-ray-to-charge transducer while the a-PbO acts as a lag prevention layer. The hole mobility in the a-PbO/poly-PbO bilayer structure was measured by photo-Charge Extraction by Linearly Increasing Voltage technique at different temperatures and electric fields to investigate charge transport properties. It was found that the hole mobility is similar to that in a-Se—currently the only commercially viable photoconductor for the direct conversion X-ray detectors. Evaluation of the X-ray temporal performance demonstrated complete suppression of signal lag, allowing operation of the a-PbO/poly-PbO detector in real-time imaging. [ABSTRACT FROM AUTHOR]

An approach for the determination of the distribution of density of electronic states in organic photoconductors is proposed. It is based on the analysis of absorption coefficient spectral dependence and the photoconductivity temperature dependence of photosensitive thin solid films. Feasibility of the approach is demonstrated by a study of the dependences using co-polymer of phenylquinoline derivative and 2,1,3-benzothiadiazole as an organic photoconductor. The distributions of density of electronic states are described well by the Gaussian function, and the corresponding full-width at-half-maxima are determined. Image 1 • Determination of density of states in organic photoconductors from the analysis of optical and photoelectric properties. • Measuring the spectral dependence of the absorption coefficient by the constant photocurrent method. [ABSTRACT FROM AUTHOR]

The article presents an interview with Emilien Peytavit, THz photonics systems talks to us about low-temperature growing of GaAs ultrafast photoconductors. He talks about a little bit about his field of research; and what challenges did you have to overcome during the research for your Letter. He describe the background to the work that is presented in his Electronics Letters submission.

A zinc oxide (ZnO) nanowire photodetector was fabricated by a simple method of growing ZnO nanowires bridging the gap of two patterned zinc electrodes. The nanowire growth is self-catalytic, involving the direct heating of patterned Zn electrodes at 700 °C in an O2/Ar gas flow of 20 SCCM (standard cubic centimeter per minute at STP)/80 SCCM, respectively, at atmospheric pressure for 3 h. The fabricated photodetector demonstrated fast response of shorter than 0.4 ms to UV illumination in air, which could be attributed to the adsorption, desorption, and diffusion of water molecules in the air onto the nanowire significantly influencing the photoresponse. [ABSTRACT FROM AUTHOR]

We have fabricated one kind of organic photocoupler with organic light-emitting diode as the input unit and pentacene photoresistor as the output unit. The wavelength of the emitting light was 522 nm. The output current of the photocoupler linearly increased with its input current and the ratio of the transfer current density reached 3. When the output voltages were 60 V, the ratio of the maximum output current to the minimum output current was 150. The breakdown voltage between the input unit and the output unit was more than 10 kV and the response time of the device was about 6.5 s. We believe this kind of device is promising in the full organic optoelectronic integrated circuits. [ABSTRACT FROM AUTHOR]

The absorption coefficient of thick-films of the negative photoresist SU-8 is observed to be time dependent during photolithographic exposure by I-line ultraviolet light (λ=365 nm); varying linearly from 38±1 cm-1 to 49±1 cm-1 for a surface exposure dose of 415 mJ/cm2. We develop a general model which enables the exposure dose to be calculated at a given photoresist depth for a given exposure time. We determine the critical exposure dose for the subsequent polymerization of SU-8 having an arbitrary thickness to be 49.4±3.9 mJ cm-2. [ABSTRACT FROM AUTHOR]

Deals with the measurement performance of a toy car under force of gravity. Equations of motion; Characteristics of a photoresistor timing system; Layout design of the track.

A novel phototransistor is fabricated by placing Si[sub 0.5]Ge[sub 0.5]/Si multiple quantum wells (MQWs) between the base and the collector of Si-SiGe heterojunction bipolar transistors (HPT). The SiGe-Si MQWs are used as a light absorption layer. The cutoff frequency (f[sub T]) and maximum oscillation frequency (f[sub MAX]) of the phototransistor are found to be 25 GHz, which is suitable for gigabit integrated circuit. The responsivity of 1.3 A/W (external quantum efficiency = 194%) and the pulsewidth of 184 ps at a wavelength of 850 nm are observed. The excellent electrical and optical performance of the Si-SiGe MQW phototransistor makes it attractive for future Si-based optoelectronic integrated circuit applications. [ABSTRACT FROM AUTHOR]

Examines the use of simple spectrophotometer in capstone circuit for an electronics laboratory exercise. Fundamentals of electronics; Construction of a low cost device to measure polymer conductivity; Evaluation of the response of the photoresistor.