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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Negative annealing in silicon after the implantation of high-energy sodium ions

The implantation of sodium ions with an energy of 300 keV is carried out into high-resistivity p-Si. The annealing of defects at T{sub ann} = 350–450°C and related activation of atoms (the latter occurs at the “tail” of atom distribution) are described by a first-order reaction. At T{sub ann} = 450–525°C and irrespective of the ion dose, negative annealing is observed; this annealing is accompanied by an appreciable increase in the surface resistance ρ{sub s}. According to estimations, the activation energy of this process amounts to ~2 eV. It is our opinion that the annealing is related to the precipitation of sodium donor atoms, which occurs at a depth exceeding by two–three times the projected range R{sub p} of ions. The annealing of defects at T{sub ann} = 525–700°C, which leads to a further decrease in ρ{sub s}, features an activation energy of ~2.1 eV. The hypothesis that the “tail” in the profiles of sodium atoms measured by secondary-ion mass spectroscopy is due to the diffusion of these atoms from the walls of the crater to its center is verified. It is shown that this process is not implemented since the profiles of sodium atoms measured at room temperature do not differ from those measured at–140°C.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Improvement in the photocurrent collection due to enhanced absorption of light by synthesizing staggered layers of silver nanoclusters in silicon

The quest for increased efficiency of solar cells has driven the research in synthesizing photovoltaic cells involving Si based materials. The efficiency of solar cells involving crystalline Si is stalled around 25% for the last decade. Recently Shi et al. had shown that light trapping can be enhanced by fabricating double layers of Ag nanoparticles in silicon based materials. The light trapping is critically important in a photo devices such as solar cells in order to increase light absorption and efficiency. In the present work, we report enhancement in the absorption of light in Ag ion implanted Si substrates. Multiple low energies Ag ions, ranging from ∼80 keV to ∼30 keV, with different fluences ranging from ∼1 × 10{sup 16} to ∼1 × 10{sup 17} atoms/cm{sup 2} were sequentially implanted into commercially available Si (100) substrates followed by post-thermal annealing to create different sizes of Ag nanoclusters (NC) at different depths in the top 100 nm of the Si. The absorbance of light is increased in Ag implanted Si with a significant increase in the current collection in I-V (current-voltage) photo switching measurements. The experimental photovoltaic cells fabricated with the Ag-implanted Si samples were optically characterized under AM (air mass) 1.5 solar radiation conditions (∼1.0 kW/m{sup 2}). An enhancement in the charge collection were measured in the annealed samples, where prominent Ag NCs were formed in the Si matrix compared to the as-implanted samples with amorphous layers. We believe the enhancement of the photo-current density from the samples with Ag NC is due to the improvement of efficiency of charge collection of e{sup −}-h{sup +} pairs produced by the incident light.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Dose Dependence of Nanocrystal Formation in Helium-Implanted Silicon Layers

The possibility of nanocrystal formation in silicon layers subjected to plasma-immersion helium-ion implantation at an energy of 5 keV has been proved for the first time. The effect of the implantation dose on the microstructure of the layers has been studied by X-ray reflectometry, transmission electron microscopy and Raman scattering. It has been established that the formation of silicon nanocrystals with dimensions of 10–20 nm is accompanied by a pronounced dependence on the ion flux and occurs at a dose of 5 × 10{sup 17} cm{sup –2} with subsequent annealing at 700–800°C. The excessive dose has been shown to cause the destruction of the upper protective sublayer and the degradation of the optical properties of nanocrystals.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Lattice modification in KTiOPO{sub 4} by hydrogen and helium sequentially implantation in submicrometer depth

We investigated lattice modification and its physical mechanism in H and He co-implanted, z-cut potassium titanyl phosphate (KTiOPO{sub 4}). The samples were implanted with 110 keV H and 190 keV He, both to a fluence of 4 × 10{sup 16 }cm{sup −2}, at room temperature. Rutherford backscattering/channeling, high-resolution x-ray diffraction, and transmission electron microscopy were used to examine the implantation-induced structural changes and strain. Experimental and simulated x-ray diffraction results show that the strain in the implanted KTiOPO{sub 4} crystal is caused by interstitial atoms. The strain and stress are anisotropic and depend on the crystal's orientation. Transmission electron microscopy studies indicate that ion implantation produces many dislocations in the as-implanted samples. Annealing can induce ion aggregation to form nanobubbles, but plastic deformation and ion out-diffusion prevent the KTiOPO{sub 4} surface from blistering.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Kinetics of Coloration in Hydrogenated Vanadium Pentoxide Films under an Internal Electrochromic Effect

The kinetics of coloration in thin hydrogenated vanadium pentoxide films under the internal electrochromic effect is studied alongside with the influence of their hydrogenation by means of plasma-immersion ion implantation on this process. The variant of uniform implantation and the nonuniform case when a film is partially subjected to ion treatment are considered. Based on the experiments on measuring the electrochromically colored surface area growth rate and the passing current, it has been revealed that the electrochromic effect becomes much stronger in the nonuniform variant, when the cathode is placed on the nonhydrogenated part of a film, and the anode is located on its hydrogenated part.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Temperature sensor based on a polymer diffraction grating with silver nanoparticles

The method is suggested for producing an optical temperature noncontact sensor on a polymer polymethylmethacrylate (PMMA) substrate with a diffraction optical element formed by implanting low-energy high-dose silver ions through a surface mask. Ion implantation is performed at an energy of 30 keV, a radiation dose of 5.0 × 10{sup 16} ion cm{sup −}2 and an ion beam current density of 2 μA cm{sup −}2 through a surface metal mask having the form of grid with square periodical holes (cells) of size 25 μm. In the course of implantation, silver nanoparticles are produced in periodical unmasked domains of irradiated PMMA. Operation of the temperature sensor on diffraction microstructures made of polymer with silver nanoparticles is demonstrated in the range from 20 °C to 95 °C by testing it with a probe radiation of a He – Ne laser. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Electrical properties and dielectric spectroscopy of Ar{sup +} implanted polycarbonate

The aim of the present paper is to study the effect of argon ion implantation on electrical and dielectric properties of polycarbonate. Specimens were implanted with 130 keV Ar{sup +} ions in the fluence ranging from 1×10{sup 14} to 1×10{sup 16} ions cm{sup −2}. The beam current used was ∼0.40 µA cm{sup −2}. The electrical conduction behaviour of virgin and Ar{sup +} implanted polycarbonate specimens have been studied through current-voltage (I-V characteristic) measurements. It has been observed that after implantation conductivity increases with increasing ion fluence. The dielectric spectroscopy of these specimens has been done in the frequency range of 100 kHz-100 MHz. Relaxation processes were studied by Cole-Cole plot of complex permittivity (real part of complex permittivity, ε′ vs. imaginary part of complex permittivity, ε″). The Cole-Cole plots have also been used to determine static dielectric constant (ε{sub s}), optical dielectric constant (ε{sub ∞}), spreading factor (α), average relaxation time (τ{sub 0}) and molecular relaxation time (τ). The dielectric behaviour has been found to be significantly affected due to Ar{sup +} implantation. The possible correlation between this behaviour and the changes induced by the implantation has been discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1982

New implantation techniques for improved solar cell junctions

Ion implantation techniques offering improved cell performance and reduced cost have been studied. These techniques include non-mass-analyzed phosphorus implantation, argon implantation gettering, and low temperature boron annealing. It is found that cells produced by non-mass-analyzed implantation perform as well as mass-analyzed controls, and that the cell performance is largely independent of process parameters. A study of argon implantation gettering shows no improvement over non-gettered controls. Results of low temperature boron annealing experiments are presented.

Spitzer, M. B.↗
DOE OSTI2018

Matrix Calculation of the Spectral Characteristics of AII–BVI Semiconductors Doped with Iron-Group Ions

A method for the matrix calculation of the spectral characteristics of AII–BVI semiconductors doped with iron-group ions is proposed, which takes into account all possible interactions in the ion and the effect of intramolecular surrounding fields of different symmetries. A technique for calculating the oscillator strength on the basis of eigenfunctions of the resulting states of 3d{sup 7}, 3d{sup 8}, and 3d{sup 6} electron configurations is developed. The spectral regularities of the Co{sup 2+}, Ni{sup 2+}, and Fe{sup 2+} energy structures for the ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, and CdTe materials are studied. All possible spectral bands in iron-group ions implanted in AII–BVI semiconductors in the range of 1.3–3 μm are established. The possibility of implementing the laser effect on these materials is estimated.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Lithium implantation at low temperature in silicon for sharp buried amorphous layer formation and defect engineering

The crystalline-to-amorphous transformation induced by lithium ion implantation at low temperature has been investigated. The resulting damage structure and its thermal evolution have been studied by a combination of Rutherford backscattering spectroscopy channelling (RBS/C) and cross sectional transmission electron microscopy (XTEM). Lithium low-fluence implantation at liquid nitrogen temperature is shown to produce a three layers structure: an amorphous layer surrounded by two highly damaged layers. A thermal treatment at 400 Degree-Sign C leads to the formation of a sharp amorphous/crystalline interfacial transition and defect annihilation of the front heavily damaged layer. After 600 Degree-Sign C annealing, complete recrystallization takes place and no extended defects are left. Anomalous recrystallization rate is observed with different motion velocities of the a/c interfaces and is ascribed to lithium acting as a surfactant. Moreover, the sharp buried amorphous layer is shown to be an efficient sink for interstitials impeding interstitial supersaturation and {l_brace}311{r_brace} defect formation in case of subsequent neon implantation. This study shows that lithium implantation at liquid nitrogen temperature can be suitable to form a sharp buried amorphous layer with a well-defined crystalline front layer, thus having potential applications for defects engineering in the improvement of post-implantation layers quality and for shallow junction formation.

36 MATERIALS SCIENCE↗
NASA NTRS1989

Diamondlike carbon protective coatings for optical windows

Diamondlike carbon (DLC) films were deposited on infrared transmitting optical windows and were evaluated as protective coatings for these windows exposed to particle and rain erosion. The DLC films were deposited on zinc selenide (ZnSe) and zinc sulfide (ZnS) by three different ion beam methods: (1) sputter deposition from a carbon target using an 8-cm argon ion source; (2) direct deposition by a 30-cm hollow cathode ion source with hydrocarbon gas in argon; and (3) dual beam direct deposition by the 30-cm hollow cathode ion source and an 8-cm argon ion source. In an attempt to improve the adherence of the DLC films on ZnSc and ZnS, ion beam cleaning, ion implantation with helium and neon ions, or sputter deposition of a thin, ion beam intermediate coating was employed prior to deposition of the DLC film. The protection that the DLC films afforded the windows from particle and rain erosion was evaluated, along with the hydrogen content, adherence, intrinsic stress, and infrared transmittance of the films. Because of the elevated stress levels in the ion beam sputtered DLC films and in those ion beam deposited with butane, films thicker than 0.1 micron and with good adherence on ZnS and ZnSe could not be generated. An intermediate coating of germanium successfully allowed the DLC films to remain adherent to the optical windows and caused only negligible reduction in the specular transmittance of the ZnS and ZnSe at 10 microns.

Swec, Diane M.↗
NASA NTRS1989

Diamondlike carbon protective coatings for optical windows

Diamondlike carbon (DLC) films were deposited on infrared transmitting optical windows and were evaluated as protective coatings for these windows exposed to particle and rain erosion. The DLC films were deposited on zinc selenide (ZnSe) and zinc sulfide (ZnS) by three different ion beam methods: (1) sputter deposition from a carbon target using an 8-cm argon ion source; (2) direct deposition by a 30-cm hollow cathode ion source with hydrocarbon gas in argon; and (3) dual beam direct deposition by the 30-cm hollow cathode ion source and an 8-cm argon ion source. In an attempt to improve the adherence of the DLC films on ZnSc and ZnS, ion beam cleaning, ion implantation with helium and neon ions, or sputter deposition of a thin, ion beam intermediate coating was employed prior to deposition of the DLC film. The protection that the DLC films afforded the windows from particle and rain erosion was evaluated, along with the hydrogen content, adherence, intrinsic stress, and infrared transmittance of the films. Because of the elevated stress levels in the ion beam sputtered DLC films and in those ion beam deposited with butane, films thicker than 0.1 micron and with good adherence on ZnS and ZnSe could not be generated. An intermediate coating of germanium successfully allowed the DLC films to remain adherent to the optical windows and caused only negligible reduction in the specular transmittance of the ZnS and ZnSe at 10 microns.

Swec, Diane M.↗
DOE OSTI2016

Stopping characteristics of boron and indium ions in silicon

The mean range and its standard deviation are calculated for boron ions implanted into silicon with energies below 10 keV. Similar characteristics are calculated for indium ions with energies below 200 keV. The obtained results are presented in tabular and graphical forms. These results may help in the assessment of conditions of production of integrated circuits with nanometer-sized elements.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1993

Mass loading and velocity diffusion models for heavy pickup ions at comet Grigg-Skjellerup

We compare model predictions of cometary water group ion densities and the solar wind slow down with measurements made by the Giotto Johnstone plasma analyzer implanted ion sensor at the encounter with comet Grigg-Skjellerup (G-S) on July 10, 1992. The observed slope of the ion density profile on approach to the comet is unexpectedly steep. Possible explanations for this are discussed. We present also a preliminary investigation of the quasilinear velocity-space diffusion of the implanted heavy ion population at G-S using a transport equation including souce, convection, adiabatic compression, and velocity diffusion terms. Resulting distributions are anisotropic, in agreement with observations. We consider theoretically the waves that may be generated by the diffusion process for the observed solar wind conditions. At initial ion injections, waves are generated at omega approximately Omega(sub i) the ion gyrofrequency, and lower frequencies are predicted for diffusion toward a bispherical shell.

Huddleston, D. E.↗
DOE OSTI2016

Optical and electronic properties of sub-surface conducting layers in diamond created by MeV B-implantation at elevated temperatures

Boron implantation with in-situ dynamic annealing is used to produce highly conductive sub-surface layers in type IIa (100) diamond plates for the search of a superconducting phase transition. Here, we demonstrate that high-fluence MeV ion-implantation, at elevated temperatures avoids graphitization and can be used to achieve doping densities of 6 at. %. In order to quantify the diamond crystal damage associated with implantation Raman spectroscopy was performed, demonstrating high temperature annealing recovers the lattice. Additionally, low-temperature electronic transport measurements show evidence of charge carrier densities close to the metal-insulator-transition. After electronic characterization, secondary ion mass spectrometry was performed to map out the ion profile of the implanted plates. The analysis shows close agreement with the simulated ion-profile assuming scaling factors that take into account an average change in diamond density due to device fabrication. Finally, the data show that boron diffusion is negligible during the high temperature annealing process.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Optimization of a low noise detection circuit for probing the structure of damage cascades with IBIC

Optimal detector / pre-amplifier combinations have been identified for the use of light ion IBIC (ion beam induced charge) to probe the physical structure of electrically active defects in damage cascades caused by heavy ion implantation. The ideal detector must have a sufficiently thin dead layer that incident ions will produce the majority of damage cascades in the depletion region of the detector rather than the dead layer. Detector and circuit noise must be low enough to detect the implantation of a single heavy ion as well as the decrease in the light ion IBIC signal caused by Shockley-Read-Hall recombination when the beam scans regions of the detector damaged by the heavy ion. The IBIC signals from three detectors irradiated with 750 keV He⁺ ions are measured with commercial and bespoke charge sensitive pre-amplifiers to identify the combination with the lowest noise.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗