Thin-film Detectors Research Articles

TSEE Response of BeO Thin Film Detectors Irradiated on ISO Rod Phantoms to Photons and Beta Radiation

Working Group 2 of the International Organisation for Standardisation (ISO) recommends a cylindrical PMMA (rod) phantom of 19 mm in diameter for the calibration of extremity dosemeters. Exoelectron emitting BeO thin film detectors on graphite substrates, covered with a polypyrrole foil of 6.7 mg.cm-2, were exposed on this rod phantom to photons and beta radiation for response assessment. Exposures to photons were carried out with heavily filtered X rays of various energies, 137Cs and 60Co, exposures to beta radiation with 90Sr/90Y, 204Tl and 147Pm. For perpendicular radiation incidence the results are related to measurements free-in-air, the angular dependence of the response to photons is compared with calculated data of Hp(0.07,a). For beta radiation the measured Hp(0.07,a) values are, within the margins of measurement uncertainty, comparable with the corresponding values achieved on the commonly used slab phantom. Certain discrepancies at larger angles of radiation incidence are caused by attenuation and scattering effects at the substrate side wall of 0.4 mm height around the TSEE sensitive plane.

Heat Flow and Detectivity of Multilayer Thin-Film Pyroelectric Detector

The pyroelectric responses of a multilayer, thin-film pyroelectric detector under both isolated and heat-sink boundary conditions are completely analyzed. Exact mathematical solutions of the heat flow equation are derived. The multilayer detector is composed of pyroelectric layer/thermal isolation layer/silicon substrate. The analytical result shows that when the thickness of the isolation layer is increased, the detectivity, D*, at low frequencies will be improved, and as the thickness of the pyroelectric layer is decreased, the high-frequency response is improved. D* of a detector with 1 µm PLZT((Pb, La)(Zr, Ti)O3)/10 µm porous silica/0.5 mm silicon is higher than that of the detector with 10 µm PLZT/1 µm porous silica/0.5 mm silicon in a wide frequency range. In order to achieve better performance of a multilayer thin-film detector, the thicknesses of the two layers should be chosen very carefully. This analysis provides a guide for the preparation of multilayer thin-film pyroelectric detectors.

Thin-film multimaterial optoelectronic integrated circuits

The multimaterial integration of thin-film optoelectronic devices with host substrates ranging from silicon circuits to glass waveguides to polymer micromachines offers to the system designer the freedom to choose the optimal materials for each component to achieve performance and cost objectives. Thin-film compound semiconductor optoelectronic devices are comparable to, and, in some cases, better than, their on-wafer counterparts. Thin-film detectors have been integrated with receiver circuits and movable micromachines, thin-film emitters with drive circuitry, and both have been used to demonstrate three-dimensionally interconnected systems. Vertical electrical integration of detector arrays on top of circuits is examined for massively parallel processing of images. Vertical optical interconnections of stacked silicon circuits (which are transparent to the wavelength of light used) are explored, and are used to develop a massively parallel processing architecture based upon low memory, high throughput, and high input/output.

Large-area 1D thin-film position-sensitive detector with high detection resolution

Abstract The aim of this work is to present the main optoelectronic characteristics of large-area one-dimensional position-sensitive detectors (1D TFPSDs) based on amorphous silicon (a-Si) p-i-n diodes. From that, the device resolution, response time and detectivity (defined as being the reciprocal of the noise equivalent power pattern) are derived and discussed concerning the field of applications of the 1D TFPSDs.

Static behaviour of thin-film position-sensitive detectors based on p-i-n a-Si:H devices

Abstract The aim of this work is to provide the basis for the interpretation of the lateral photoeffect in p-i-n a-Si:H one-dimensional thin-film position-sensitive detectors (1D TFPSDs) under steady state, through an analytical model. The experimental data recorded in 1D TFPSD devices with different characteristics are compared with the predicted curves and the obtained correlations are discussed.

Communication through stacked silicon circuitry using integrated thin film InP-based emitters and detectors

To demonstrate optical communication through stacked silicon circuitry, thin film InGaAsP-based emitters and photodetectors have been bonded directly onto silicon circuitry. These optoelectronic devices operate at a wavelength to which silicon is transparent. The thin film emitters and detectors were integrated onto a MOSIS foundry silicon CMOS integrated circuit which contained driver and amplifier circuits. Bidirectional vertical optical communication between two layers of circuitry was demonstrated by stacking the layers, exciting the emitter driver circuit on one layer with an electrical signal, and measuring the output electrical signal from the detector amplifier located on the other circuit in the vertical stack.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Properties of PLT thin film pyroelectric detectors I. Current responsivity

By solving the one-dimensional heat conduction equation, the dynamic pyroelectric response of a thin film pyroelectric detector to sinusoidal modulated radiation is represented by a matrix. The influence of the parameters of each layer in the detector on the current responsivity is analyzed. Theoretical results are compared with the experimental results for PLT thin film detectors.

Measurement of Fragment Mass Dependent Kinetic Energy and Neutron Multiplicity for Thermal Neutron Induced Fission of Plutonium-239

Kinetic energy and neutron multiplicity as a function of fragment mass were measured for the thermal neutron induced fission of 239Pu. By measuring the velocities and energies of two fission fragments simultaneously, both of the pre-neutron emission fragment mass m* and the post-neutron mass m were obtained. The fragment mass dependent neutron multiplicity ν(m*) was deduced by subtracting m from m*. The fragment mass dependent total kinetic energy TKE(m*) was also obtained from this data. The fragment velocity was measured by time-of-flight (TOF) method, for which the start signal was triggered by a very thin plastic scintillation film detector (TFD) and the stop signal was obtained by a silicon surface barrier detector (SSBD) which was also used for the measurement of [he fragment kinetic energy. The present result of ν(m*) is in good agreement with that of Apalin et al. and that in the light fragment region of Fraser et al. The obtained TKE(m*) agrees well with the data of Wagemans et al. A calculation was carried out with the model proposed by Brosa et al. who assumed multichannel fission paths and a random neck rupture. It is seen that the calculated results of both fragment mass dependent kinetic energy and neutron multiplicity represent experimental data well.

Measurement of Fragment Mass Dependent Kinetic Energy and Neutron Multiplicity for Thermal Neutron Induced Fission of Plutonium-239.

Kinetic energy and neutron multiplicity as a function of fragment mass were measured for the thermal neutron induced fission of 239Pu. By measuring the velocities and energies of two fission fragments simultaneously, both of the pre-neutron emission fragment mass m* and the post-neutron mass m were obtained. The fragment mass dependent neutron multiplicity ν(m*) was deduced by subtracting m from m*. The fragment mass dependent total kinetic energy TKE(m*) was also obtained from this data. The fragment velocity was measured by time-of-flight (TOF) method, for which the start signal was triggered by a very thin plastic scintillation film detector (TFD) and the stop signal was obtained by a silicon surface barrier detector (SSBD) which was also used for the measurement of [he fragment kinetic energy. The present result of ν(m*) is in good agreement with that of Apalin et al. and that in the light fragment region of Fraser et al. The obtained TKE(m*) agrees well with the data of Wagemans et al. A calculation was carried out with the model proposed by Brosa et al. who assumed multichannel fission paths and a random neck rupture. It is seen that the calculated results of both fragment mass dependent kinetic energy and neutron multiplicity represent experimental data well.

Organically Modified SiO2 and Al2O3 Films as Selective Components for Gas Sensors

Pure SiO2 and Al2O3 films and organically modified SiO2 layers are deposited by three different CVD techniques on SnO2 thin-film gas detectors. Ion-beam-assisted deposition (IBAD) of TEOS and ph-TEOS under bombardment with argon or oxygen ions is found to be suitable for the preparation of organically modified SiO2 membranes at room temperature. The intended selective function of the membranes for gas detection is proved. A size selective mechanism is found to be dominant, primarily controlled by the thickness of the films independent of the type of the membrane. The thickness is the most important parameter to design a membrane of specific selectivity. Smaller effects are induced by the chemistry of the membranes which nevertheless may be suitable to distinguish between molecules of comparable size. Although the organic modifications are not stable at the operation temperature of the sensors, the initial incorporation seems to be capable to tailor ceramic membranes with different properties.

Integration of thin film optoelectronic devices onto micromachined movable platforms

The integration of a thin film optoelectronic device onto a micromachined movable platform is reported in this letter. This micro-opto-mechanical system, consisting of a thin film AlGaAs/GaAs double heterostructure p-i-n detector integrated onto a polyimide micromachined platform on silicon, has applications which range from fiber optic coupling to sensors. Fiber optic coupling is demonstrated using a stationary fiber positioned above the thin film detector. By applying a voltage between the platform and actuation strips, the platform moves and a change in fiber to detector coupling is observed. >

Applications of cyclotron based ion scattering

Ion scattering experiments have been performed with a 3–30 MeV AVF cyclotron. The wide range of available energies combined with proper beam handling allows many scattering techniques to perform. At first an example of ordinary Rutherford backscattering spectrometry will be demonstrated on model catalysts as studied in surface chemistry. High energy backscattering spectrometry with 8.8 MeV He ions, which enhances the sensitivity for oxygen, has been applied to study the oxygen removal from corroded archaeological artefacts upon treatment with a H 2 plasma. Elastic recoil detection analysis will be shown feasible with He ions having incident energies between 10 and 15 MeV once combined with a thin film detector. The development of a setup for ion channeling experiments with the cyclotron is reported and first results promise to increase the angular resolution in lattice deformation studies.

Effects of the Multilayer Structure on the Responsivity of Pyroelectric Thin Film Detectors

AbstractPyroelectric thin film detectors have advantages of wavelength independent sensitivity, room temperature operation and direct incorporation with integrated circuit amplifiers. Pyroelectric thin films with good quality have be prepared by many advanced thin film technologies [1-2]. The responsivity of pyroelectric thin film detectors is dependent on the thermal properties of the substrate, on which pyroelectric thin film detectors are prepared. The heat conduction in the detectors was investigated using the one-dimensional heat flow equation and the expressions describing the detectors performance were derived for pyroelectric thin films detectors with multilayer structure. The numerical simulation showed that the pyroelectric thin film detectors need effective heat isolation. If the air gap could be the heat isolation layer, which is between the bottom electrode and substrate, the iesponsivity of detectors would be higher than that of detectors which have no heat isolation in certain modulation frequency range.

Thermophysical Measurements and Interfacial Adhesion Studies in Ultrathin Polymer Films Using Homodyne Photothermal Spectrometry

Homodyne laser photopyroelectric spectrometry (PPES) is a new photothermal detection scheme which uses electronic mixing to downshift a high-frequency swept wave photothermal response into a bandwidth of approximately one kilohertz. A rapid photopyroelectric impulse response is recovered from the downshifted component at high time resolution and is used, here, in two different geometries, to probe the thermal and interfacial properties of assemblies composed of submicron-thick-ness polymer films deposited on the metallized surface of a pyroelectric thin-film detector. In the thermal transmission mode geometry, the sample is excited by irradiation in a very thin opaque surface layer, and the transit time of a heat pulse through the sample to the pyroelectric transducer can be used to obtain a thickness or thermal diffusivity measurement. By the use of an inverse mode geometry, a metal/polymer interface is excited by irradiation of an optically transparent polymer thin-film sample attached to the metallized surface of the pyroelectric transducer. Heat flow at short distances from the bond interface can be monitored by the pyroelectric effect through the high time resolution of the homo-dyne photopyroelectric measurement. The combination of information obtained in these two geometries with an analysis of the thermal wave reflections which occur at interfaces between materials of dissimilar thermal effusivity can be used to evaluate relative interfacial adhesion between the metal and polymer layer.

Vertical optical communication through stacked silicon wafers using hybrid monolithic thin film InGaAsP emitters and detectors

The authors report the first demonstration of vertical optical communication through stacked Si wafers using low-cost hybrid monolithic thin-film InGaAsP/InP emitters and detectors, designed for operation at 1.3 mu m. A thin-film InGaAsP homojunction light-emitting diode (LED) (4.5- mu m thick) was deposited onto a polished, nitride-coated Si wafer using a modified epitaxial liftoff technique. A InP/InGaAsP/InP p-i-n photodetector (4.5- mu m thick) was similarly deposited on an identically prepared Si wafer. The emitter and detector were then aligned, resulting in a stacked wafer configuration suitable for vertical through-wafer optical communication. This integration technique eliminates the need for direct growth of compound semiconductors onto Si. >

Determination of nuclear charge resolution of a thin film detector using a 252Cf fission fragment source

Little quantitative information is available regarding the ability of a thin film detector (TFD) to determine the nuclear charge of a low energy heavy mass ion. To compare the nuclear charge resolving power Z / ΔZ of the TFD to other heavy ion detectors, an experiment was performed where the TFD luminescence response to 252 Cf fission fragments was recorded in coincidence with the gamma de-excitation of the fragments. With this technique, the TFD nuclear charge resolving power Z / ΔZ was determined to be 25.2 for the light mass fragment group.

Performance of a three-element thin film detector

A nuclear charged particle detector has been designed and fabricated at the University of Florida for use in identifying the nuclear charge Z and mass number A of low energy (∼1 MeV/amu) heavy mass ions. The detector consists of a stack of three sequential thin film detectors (made from NE-102A plastic scintillator) for three successive measurements of the specific luminescence ΔL/ Δx and velocity of a transiting ion and a terminal surface barrier detector for measuring the ion residual energy. This detector assembly was tested by measuring its response to various isotopes of germanium and selenium ions accelerated to selected energies between 53 and 169 MeV and then scattered from a thin gold target foil. The tests were performed to obtain quantitative information on the ability of the detector system to identify the nuclear Z of an impinging ion and to test the 0810 1076 V 3 advantage of having three successive measurements of ΔL/ Δx from three sequential and independent thin film detectors. It was determined that below 2 MeV/amu the detector response was dependent on particle velocity but independent of particle mass and below about 0.9 MeV/amu the detector was not able to distinguish between ions having two units difference in Z, probably due to similarities in ionic charge state distributions. It was also determined that the use of three detectors reduced the FWHM of the TFD response by 54%.

Vertical electrical interconnection of compound semiconductor thin-film devices to underlying silicon circuitry

A three-dimensional integration technology that electrically connects an independently optimized thin-film device layer to a Si circuitry layer is reported. An epitaxial liftoff GaAs thin-film optical detector is integrated directly on top of Si amplifier circuitry with a planarizing, insulating layer of polymide between the detector and the circuitry. The detector is virtually connected to the circuitry below through an electrical via in the insulator. This integration technology enables monolithic, massively parallel vertical interconnection between two independently optimized device layers. Systems such as image processing arrays should significantly benefit from this massively parallel integration technology. >

Impulse Photopyroelectric Depth Profiling of Multilayers. Part II: Experiments with Amplitude- and Phase-Modulated Wideband Spectrometry

Impulse response photopyroelectric effect spectrometry (PPES) was implemented with the use of wideband excitation for the recovery of depth profiles of optical absorption in a series of multilayered thin-film polymer samples. The wideband PPES technique intensity modulates a cw laser beam with a waveform whose power spectrum is flat over the photothermal response bandwidth, enabling the recovery of the PPES impulse response (short pulse equivalent) by correlation and spectral analysis techniques. The impulse response measurement recovers a depth profile of subsurface optical absorption through the spatial dependence of the heat flux deposited in the sample by a short optical pulse. It shows excellent potential for use as a nondestructive evaluation tool in the analysis of polymers. The impulse response data recovered in this work could be accounted for by means of a theoretical model which neglected thermal reflections between the constituent sample layers. Absorption coefficient measurements on a single-layer sample were recovered through the time delay dependence of the PPES impulse response. The data were corrected for the effect of reflectivity at the thin-film pyroelectric detector surface, which significantly affects the time dependence of the impulse response. Several types of measurements were demonstrated on optically inhomogeneous samples. These included measurements of the thickness of transparent overlayers deposited on opaque substrates, depth-resolved spectroscopy, and techniques for improving multilayer contrast. The role of thermal wave reflections at the gas/solid interface was identified as a key factor in determining the depth profile contrast for subsurface spectral contributions, as well as the dependence of the impulse response on the thickness of nonabsorbing overlayers. Several approaches for optimizing photothermal depth profile contrast were demonstrated.

Photopyroelectric measurement of the thermal diffusivity of YBa2Cu3O7-xAND Bi2Sr2CaCu2Ox

Abstract Thermal diffusivity measurements for superconducting YBa2Cu3O7-x and Bi2Sr2CaCu2Ox are reported over the temperature range from 50 to 300 K. The results were obtained using frequency-modulated time-delay photopyroelectric spectrometry (FM-TDPS), which consists of chirped laster excitation of the sample and detection of the associated impulse by a thin-film pyroelectric detector.