Surface Barrier Semiconductor Research Articles

Continuous monitoring experiment of soil radon levels using a semiconductor-based measuring instrument

Soil radon measurement is crucial for environmental safety, public health, and earth science research. Despite significant advancements in the development of radon measurement instruments and methods, there is still a lack of instruments for continuous soil radon monitoring. Therefore, we have developed a continuous radon measurement instrument and designed a corresponding field installation method. This instrument uses a gold-silicon surface barrier semiconductor electrostatic method to measure radon exhalation concentration from the soil and achieves automatic sampling via natural air diffusion. It operates on solar power, is easy to install, and supports both wireless and wired communication. Multiple instruments have been continuously tested in the field for more than a year, showing consistent data among adjacent instruments and the ability to reveal the fluctuation patterns of soil radon. However, practical applications have encountered some challenges, such as data noise and the impact of condensate water on the detector surface.

Nuclear Reactions under Irradiation of Deuterated Structures by X Rays

Measurements of emission from nuclear reaction products (neutrons and protons) have been carried out appearing in the deuterated structures of textured CVD diamond, palladium, titanium, and zirconium under irradiation with a beam of X rays using independent methods (neutron detector based on He-3 counters, Si surface-barrier semiconductor detectors and CR-39 track detector). The possibility of enhancement of both DD reaction and multi-particle deuterium fusion by the beam of X rays with energy ranging 20–30 keV in solid deuterated targets has been established. Analysis of X-ray fluorescence spectra of the target bombarded by beams of ions has revealed “additional” peaks, the occurrence of which cannot be related to any of the known elements, and requires separate study.

Surface–barrier heterojunctions TiO2/CdZnTe

This paper reports the results of an investigation into electrical and photoelectrical properties of anisotype heterojunctions n-TiO2/p-Cd1-xZnxTe prepared by the dc reactive magnetron deposition of TiO2 thin films with n-type conductivity onto freshly cleaved p-Cd1-xZnxTe single crystal substrates. The heterojunctions were established to be abrupt surface–barrier semiconductor structures with the uniform distribution of uncompensated acceptors within the space charge region, which is located in the narrow-band semiconductor. The dominating mechanisms of charge transport were analyzed in the scope of tunnel-recombination processes via interface states and complex defects (V−2CdD+)−1 at forward and reverse biases. The main photoelectric parameters and the spectral distribution of actual quantum efficiency were measured at room temperature.

Electronic Contact Deposition onto Organic Molecular Monolayers: Can We Detect Metal Penetration?

AbstractUsing a semiconductor as the substrate to a molecular organic layer, penetration of metal contacts can be clearly identified by the study of electronic charge transport through the layer. A series of monolayers of saturated hydrocarbon molecules with varying lengths is assembled on Si or GaAs and the junctions resulting after further electronic contact is made by liquid Hg, indirect metal evaporation, and a “ready‐made” metal pad are measured. In contrast to tunneling characteristics, which are ambiguous regarding contact penetration, the semiconductor surface barrier is very sensitive to any direct contact with a metal. With the organic monolayer intact, a metal–insulator–semiconductor (MIS) structure results. If metal penetrated the monolayer, the junction behaves as a metal–semiconductor (MS) structure. By comparing a molecule‐free interface (MS junction) with a molecularly modified one (presumably MIS), possible metal penetration is identified. The major indicators are the semiconductor electronic transport barrier height, extracted from the junction transport characteristics, and the photovoltage. The approach does not require a series of different monolayers and data analysis is quite straightforward, helping to identify non‐invasive ways to make electronic contact to soft matter.

Development of Two Spectrometers for the Noiseless β Energy Spectrum of Radiocarbon at Room Temperature

In this work, two spectrometric methods are described to have a noiseless β energy spectrum of radiocarbon (14C) as low‐energy β emitter. The spectrometers use two timing techniques with a silicon (Si) surface barrier semiconductor detector. The experimental results are compared; they show that the methods followed in the present work were successful for obtaining a noiseless β energy spectrum.

Fast neutron spectrometer composed of PSPCs and Si(Li)-SSDs with excellent energy resolution and detection efficiency

We have developed a fast neutron spectrometer composed of three position-sensitive proportional counters (PSPCs) with methane gas and two Si(Li) surface barrier semiconductor detectors (SSDs). A collimated incident neutron beam interacts with hydrogen atoms in the methane gas to generate recoil protons. Position information of the recoil protons obtained from the PSPCs gives the recoil angle. At the same time, the energy of the recoil protons is measured with the three PSPCs and the two SSDs. Finally, the neutron energy is derived using the recoil-proton energy and the recoil angle. This spectrometer was experimentally tested using a monoenergetic neutron beam with energy of 5.0 MeV. The energy resolution and the detection efficiency were 3.5% and 1.1 times10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> %, respectively. The energy resolution could be achieved better than 2% by selecting events under proper conditions. We also developed a Monte Carlo code to evaluate the characteristics of the spectrometer. The results obtained from these simulations are compared to those obtained through experiments

The effect of temperature on the behavior of semiconductor silicon surface barrier detectors

The operating behavior of a silicon surface barrier semiconductor detector of 5 mm thick depletion depth has been studied over the temperature range from 270 to 313 K by recording the spectrum of 24.8 MeV protons. The temperature of the detector was controlled and measured by a PC-based temperature controller. The analysis of the recorded spectra shows that the centroid of the proton energy peak remains constant up to certain optimum temperature and falls down rapidly to the lower channels beyond the optimum temperature. The % resolution of the detector was found to degrade from 0.5% to 4.9%. The observed degradation is found to be related to the increase in leakage current due to rise in the detector temperature.

SPV Monitoring of Near Surface Doping – Role of Boron-Hydrogen Interaction; Boron Passivation and Reactivation

ABSTRACTHydrogen is known to cause the passivation of boron acceptors after such processing steps as wet etching, reactive ion etching, sputter deposition of metal contacts, and Ar ion beam etching. Previous studies of this effect employed CV profiling, spreading resistance profiling, and SIMS measurements on samples diffused with deuterium. These methods are either destructive to the Si surface or require deposition of metal contact. In the present study we used a non-contact small signal ac-surface photovoltage technique, currentlyavailable in commercial diagnostic tools. Simultaneous measurements of the semiconductor surface barrier, Vsb, and the capacitance of the surface depletion layer, CD, give the concentration of boron acceptors in a submicron distance from the Si surface or Si/SiO2 interface. The technique has proven very successful in monitoring low dose implants and also near surface doping in oxidized wafers. Inbare silicon wafers the method occasionally indicated surface boron concentration noticeably below the bulk value. We found such behavior in wafers after the chemical cleaning, used to prepare a hydrogen terminated surface. Thermal annealing at temperatures from 150°C to 200°C reactivates the boron dopant. We will discuss the effect of various cleaning and annealing conditions on passivation and reactivation of boron acceptors in the near surface region. The results obtained with the non-contact SPV technique show excellent agreement with previous studies. They also provide a basis for reliable measurement of the boron concentration free of interference from hydrogen passivation.

Angular distribution measurements of 12C(d,p) 13C reaction below 350 keV deuteron energies using nuclear track detectors

Angular distribution of 12C(d,p) 13C reaction were measured at 13 angles for 223, 308 and 332 keV deuteron energies using nuclear track detectors (NTDs). The measurements were carried out over 25 to 164 degree angles in 10 degree steps using scattering chamber of 80° beam line of the 350 kV accelerator. In each run, a semiconductor surface barrier (SSB) monitor detector, masked by thin mylar foil, was placed at +164 degree and was used for flux and target thickness normalization between two runs of each angular distribution. In order to check the performance of the NTDs, angular distribution measurement was also repeated at 250 keV deuteron energy at which data had already been taken with surface barrier detectors. The angular distribution measured by NTDs was found comparable with measurements carried out using SSB detectors which indicate the possibility of using NTDs instead of expensive SSB detectors. The angular distributions of 12C(d,p) 13C reaction at 223, 250, 308, and 322 keV deuteron energies are backward peaked similar to those measured using SSB detectors. Within the experimental uncertainties, the detection efficiency of PM-335 NTDs for the protons from the 12C(d,p) 13C reaction for the −164 degree angle was found to be almost 100%.

Alpha activity measurement of cigarettes in Kuwait

A semiconductor surface barrier detector with an active area of 450 mm 2 and depletion layer thickness of 300 μm has been used to measure the α activity of cigarette tobacco. The performance parameters of the counting system, the calibration and the results of α-activity in some cigarettes are presented.

THE MEASUREMENTS OF HARD X-RAY FLUCTUATIONS IN THE HT-6B TOKAMAK

Nal(Tl) scintillation detector and Si(Au) surface barrier semiconductor detector are used to measure X-ray fluctuations in the HT-6B Tokamak device. The hard X-ray emission and sawtooth oscillations have been observed. The experiment shows hard X-ray fluctuations are due to MHD disturbances in the frequency range of 2-25 kHz.

The role of nuclear track filters in radon measurements

Track dosimeters in combination with mica nuclear filters have been used to measure radon densities in a mixed atmosphere of radon and thoron. Diffusion studies were carried out in a simulated uranium/thorium mine. Radon gas concentrations were determined by alpha-counting techniques using CR-39 track detectors and surface barrier semiconductor detectors. It has been found that transmission or diffusion of radon through a mica nuclear filter depends on (a) thickness of filter, (b) area of the hole, and (c) density of holes, of the filter. Simultaneously, we studied the effect of mica nuclear filters with tiny holes (40nm<k<440nm) with respect to radon and thoron diffusion.

Measurement of the Fano factor for protons on silicon

The Fano factor for protons has been measured for silicon with a surface barrier semiconductor detector at 87 K over the energy range of E p = 0.989–4.537 MeV. The fwhm of peaks in the spectra observed were corrected for effects of plasma and of charge collection. As a result of the analysis, the value of the Fano factor was obtained as 0.16±0.04. However, the value of the corrected fwhm at E p = 0, estimated by extrapolation, cannot be accounted for by the effect of atomic collision.

The (n, α) reaction measurements on143Nd and180Hf with thermal neutrons

The thermal neutron cross sections for severalα-transitions of the143Nd(n,α) reaction have been measured using a semiconductor surface barrier telescope. The143Nd(n, γα) reaction has been observed. The180Hf(n,α) cross section estimation is given.

An experimental study of the electrical properties of the contact between two similar semiconductor crystals

Electrical measurements on pressure contacts between pairs of semiconductor crystals are reported with a view to understanding the properties of grain-grain contacts in powdered semiconductors. The materials used were Ge and GaAs, their surfaces being prepared chemically and exposed to room atmosphere. It is thus necessary to consider three contributions to the contact resistance-bulk spreading resistance, oxide film resistance and semiconductor surface barrier effects. By studying the contact resistance, shape of current voltage curves and the a.c. impedance, and comparing semiconductor-semiconductor and semiconductor-metal contacts, the following conclusions were reached: (i) for GaAs and light doped n-Ge surface barrier effects are dominant; (ii) for lightly doped p-Ge bulk spreading resistance is probably the controlling factor; (iii) for heavily doped p-Ge and oxide resistance is important.

A telescope for α-particle spectrometry

An alpha spectrometer based on a telescope consisting of two silicon semiconductor surface barrier detectors is described. The spectrometer has been used to study the α-particle energy spectra of an (n,α)-type reaction and ternary fission of uranium in an energy range 4–30 MeV with a resolution of 85 keV.

Observation of 38-334-keV Interplanetary Protons during Solar Quiet Times

The observations were from the particle experiment aboard the Apollo 16 subsatellite which was ejected April 24, 1972 into an approximately equatorial lunar orbit from the Apollo 16 lunar science module. The proton fluxes vary by a factor of about 5 over a six-month period. The proton measurements were made with a pair of surface barrier semiconductor telescopes. The accuracy of the proton flux measurements during times when electrons are present is highly dependent on the accuracy of the electronic channel matching.

Temperature response of silicon surface barrier semiconductor detectors operated in the DC--short circuit configuration.

Temperature response of silicon surface barrier semiconductor detectors operated in the DC--short circuit configuration.

Proton energy distributions from 0.060 to 3.3 Mev at 6.6 Earth radii

Proton differential fluxes are reported for 12 energies from 0.060 to 3.3 Mev at 6.6 earth radii for the time period of October 2 to 13, 1968. The proton energies were measured with a surface barrier semiconductor detector and a stacked discriminator pulse height analyzer on the Air Force Office of Aerospace Research Satellite OV2-5 (1968-81A). The typical quiettime fluxes decreased by 8 orders of magnitude over the measured energy interval. During this time the energy spectrum varied from E−3.5 to E−6.0. Below 200 kev the energy distributions flatten but never peak above the energy of the lowest channel, 68 kev. Energy spectra associated with the two magnetic storms on October 2 and 12 are presented. After the storms the fluxes were higher than before; this is particularly true at the lower energies measured. Quiettime pitch angle distributions near the local noon-midnight meridian clearly show the east-west effect caused by the radial gradient in the fluxes. The pitch angle distributions at local midnight show the ‘drift loss cone’ predicted by Roederer. This experiment provides the first confirmation of the Roederer [1967] model of shell splitting in the earth's magnetic field by measured proton angular distributions.

Mass-identification of alpha-particles and heavy ions by time-of-flight methods

A time-of-flight technique has been applied to the mass identification of heavy ions from nuclear reactions in the mass-range 4≦ A≦16. The system described consists of a zero-time detector of the secondary emission type in connection with a surface barrier semiconductor energy detector at the end of the flight path. The apparatus exhibits a time resolution of 1.15 ns for α-particles and 0.8 ns for fission-fragments, and an efficiency of 83% and 99.9%, respectively.