Anneal behavior of defects in ion-implanted GaAs diodes
Ion-implanted GaAs junction diodes anneal behavior and defect nature
Hunsperger, R. G.↗
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Results for “ION IMPLANTATION”
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Development of ion implantation techniques for microelectronics
Ion implantation forming of conducting layers and p-n junctions in gallium arsenide and silicon carbide
Dunlap, H.↗
Fabrication of Genesis Sample Simulants Using Plasma Source Ion Implantation (PSII)
Plasma source ion implantation can be used to fabricate simulant samples for the Genesis mission. These simulants will be needed by investigators to validate sample preparation and analysis techniques for the returned Genesis samples. Additional information is contained in the original extended abstract.
Kuhlman, K. R.↗
Modulating the Pseudoelastic Response of NiTi Using Ion Implantation
Ni-ion irradiated NiTi is nearly 50% harder, retains 85% recoverable deformation, and has reduced hysteresis. This work explores the feasibility of using ion beam modification to modulate the austenite to martensite phase transformation in NiTi, thereby achieving novel or localized properties in near-surface regions.
36 MATERIALS SCIENCE↗
Modulating the Pseudoelastic Response of NiTi Using Ion Implantation
Ni-ion irradiated NiTi is nearly 50% harder, retains 85% recoverable deformation, and has reduced hysteresis. This work explores the feasibility of using ion beam modification to modulate the austenite to martensite phase transformation in NiTi, thereby achieving novel or localized properties in near-surface regions.
36 MATERIALS SCIENCE↗
Physical and Tribological Characteristics of Ion-Implanted Diamond Films
Unidirectional sliding friction experiments were conducted with a natural, polished diamond pin in contact with both as-deposited and carbon-ion-implanted diamond films in ultrahigh vacuum. Diamond films were deposited on silicon, silicon carbide, and silicon nitride by microwave-plasma-assisted chemical vapor deposition. The as-deposited diamond films were impacted with carbon ions at an accelerating energy of 60 keV and a current density of 50 micron A/cm(exp 2) for approximately 6 min, resulting in a dose of 1.2 x 10(exp 17) carbon ions/cm(exp 2). The results indicate that the carbon ion implantation produced a thin surface layer of amorphous, nondiamond carbon. The nondiamond carbon greatly decreased both friction and wear of the diamond films. The coefficients of friction for the carbon-ion-implanted, fine-grain diamond films were less than 0.1, factors of 20 to 30 lower than those for the as-deposited, fine-grain diamond films. The coefficients of friction for the carbon-ion-implanted, coarse-grain diamond films were approximately 0.35, a factor of five lower than those for the as-deposited, coarse-grain diamond films. The wear rates for the carbon-ion-implanted, diamond films were on the order of 10(exp -6) mm(exp 3)/Nm, factors of 30 to 80 lower than that for the as-deposited diamond films, regardless of grain size. The friction of the carbon-ion-implanted diamond films was greatly reduced because the amorphous, nondiamond carbon, which had a low shear strength, was restricted to the surface layers (less than 0.1 micron thick) and because the underlying diamond materials retained their high hardness. In conclusion, the carbon-ion-implanted, fine-grain diamond films can be used effectively as wear resistant, self-lubricating coatings for ceramics, such as silicon nitride and silicon carbide, in ultrahigh vacuum.
Miyoshi, K.↗
Magnetization control for bit pattern formation of spinel ferromagnetic oxides by Kr ion implantation
As a first step toward the development of bit-patterned magnetic media made of oxides, we investigated the effectiveness of magnetism control by Kr implantation in a typical spinel ferromagnetic oxide, Fe{sub 3}O{sub 4}. We implanted Kr ions accelerated at 30 kV on 13-nm-thick Fe{sub 3}O{sub 4} thin films at dosages of (1–40) × 10{sup 14} ions/cm{sup 2}. Magnetization decreased with increase in ion dosages and disappeared when irradiation was greater than 2 × 10{sup 15} ions/cm{sup 2} of Kr ions. These dosages are more than ten times smaller than that used in the N{sub 2} implantation for metallic and oxide ferromagnets. Both the temperature dependence of magnetization and the Mössbauer study suggest that the transition of Fe{sub 3}O{sub 4} from ferromagnetic to paramagnetic took place sharply due to Kr ion irradiation, which produces two-phase separation—ferromagnetic and nonmagnetic with insufficient dosage of Kr ions.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Friction and Wear Properties of As-deposited and Carbon Ion-implanted Diamond Films
Recent work on the friction and wear properties of as-deposited and carbon ion-implanted diamond films was reviewed. Diamond films were produced by the microwave plasma chemical vapor deposition (CVD) technique. Diamond films with various grain sizes and surface roughnesses were implanted with carbon ions at 60 ke V ion energy, resulting in a dose of 1.2310(exp 17) carbon ions/cm(exp 2). Various analytical techniques, including Raman spectroscopy, proton recoil analysis, Rutherford backscattering, transmission and scanning electron microscopy, x-ray photoelectron spectroscopy, and x-ray diffraction, were utilized to characterize the diamond films. Sliding friction experiments were conducted with a polished natural diamond pin in contact with diamond films in the three environments: humid air (40 percent relative humidity), dry nitrogen (less than 1 percent relative humidity), and ultrahigh vacuum (10(exp -7) Pa). The CVD diamond films indeed have friction and were properties similar to those of natural diamond in the three environments. The as-deposited, fine-grain diamond films can be effectively used as self-lubricating, wear-resistant coatings that have low coefficients of friction (0.02 to 0.04) and low wear rates (10(exp -7) to 10(exp -8)mm(exp 3)/N-m) in both humid air and dry nitrogen. However, they have high coefficients of friction (1.5 to 1.7) and a high wear rate (10(exp -4)mm(exp 3/N-m) in ultrahigh vacuum. The carbon ion implanation produced a thin surficial layer (less than 0.1 micron thick) of amorphous, nondiamond carbon on the diamond films. In humid air and dry nitrogen, the ion-implanted, fine- and coarse-grain diamond films have a low coefficient of friction (around 0.1) and a low wear rate (10(exp -7)mm(exp 3/N-m). Even in ultrahigh vacuum, the presence of the nondiamond carbon layer reduced the coefficient of friction of fine-grain diamond films to 0.1 or lower and the wear rate to 10(exp -6)mm(exp 3)/N-m. Thus, the carbon ion-implanted, fine-grain diamond films can be effectively used as wear-resistant, self-lubricating coatings not only in air and dry nitrogen, but also in ultrahigh vacuum. The wear mechanism of diamond films is that of small fragments chipping off the surface. The size of wear particles is related to the extent of wear rates.
Miyoshi, Kazuhisa↗
Enhanced conduction in CdSe nanowires on 200 keV phosphorous negative ion implantation
Highlights: • CdSe nanowires were prepared by template assisted electro-deposition. • CdSe nanowires were implanted with 200 keV P{sup −} ions at different fluence. • Structure of CdSe NWs remained intact on ion implantation. • Optical band gap of CdSe NWs decreased after implantation. • The electrical conduction improved due to dominance of ionization effects. - Abstract: For II–VI compound semiconductor nanostructures, ion implantation is considered to be an area of significant interest due to its potential use in the fabrication of the extensive variety of novel optoelectric devices. CdSe nanowires with diameter 80 nm have been grown via the template-assisted electro-deposition method and were subsequently implanted with 200 keV negative phosphorous ions at fluence ranging from 10{sup 11} ions/cm{sup 2} to 10{sup 13} ions/cm{sup 2}. SRIM-TRIM simulation studies are done to understand the course and nature of events occurring during implantation. Pre- and post-implanted samples were characterized by Scanning electron microscope (SEM), X-Ray diffraction (XRD), UV–vis spectroscopy and Probe station with a Keithley source meter. Structural studies reveal no modification in crystal structure upon implantation. An increase of phosphorous content led to an apparent red shift in the optical band gap and an improvement in conductivity. These modifications are attributed to the ionization and the creation of damage on implantation.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Measurement of lattice damage caused by ion-implantation doping of semiconductors.
Discussion of two new techniques used to measure the lattice damage produced in GaAs by the implantation of 60 keV cadmium ions. In the first method, optical reflection spectra of the ion-implanted samples were measured in the wavelength range from 2000 to 4600 A. The decrease in reflectivity resulting from ion-implantation was used to determine the relative amount of lattice damage as a function of ion dose. The second technique employed the scanning electron microscope. Patterns very similar in appearance to Kikuchi electron diffraction patterns are obtained when the secondary and/or backscattered electron intensity is displayed as a function of the angle of incidence of the electron beam on a single crystal surface. The results of measurements made by both methods are compared with each other and with data obtained by the method of measuring lattice damage by Rutherford scattering of 1 MeV helium ions.
Hunsperger, R. G.↗
Modeling the impact of radiation-enhanced diffusion on implanted ion profiles
We report that ion irradiations are a valuable research tool for exploring radiation effects in materials. However, it is well recognized that the implanted ions can artificially modify the radiation damage evolution, e.g., enhancing amorphization processes at low irradiation temperatures and suppressing void swelling at elevated temperatures. Therefore, the implanted ion region should be avoided for most studies of ion irradiated materials. Due to increased interest in high damage, high temperature ion irradiations studying radiation effects in materials for proposed high dose Generation IV fission and fusion energy applications, it is crucial to quantify the extent of diffusional broadening of the implanted ion profile for a variety of temperatures, irradiation fluxes, and sink strengths. The present study summarizes computational analyses of thermal and depth-dependent radiation enhanced difusion (RED) on diffusion broadening of the implanted ion profiles in Fe and Ni for a variety of irradiation conditions. For a low assumed RED coefficient (10 -20 -10 -19 m 2 /s and 10 -4 and 10 -3 peak dpa/s, respectively) or high flux, broadening of the as-implanted ion profile is very small and a suitable artifact-free midrange region for analysis exists for ion energies above 5-6 MeV at 100 peak dpa. At high RED coefficients (10 -19 -10 -18 m 2 /s and 10 -4 and 10 -3 peak dpa/s, respectively) broadening is much more significant, and no valid region for investigation exists below 6-8 MeV ion energies at any damage level >50 dpa. While increasing flux decreases irradiation time, it also increases the RED coefficient; these effects mostly offset except under recombination-dominant conditions. For typical high dose irradiation studies of void swelling that exceed ~100 displacement per atom (dpa), ion energies > 6-8 MeV must be employed in order to achieve suitable artifact-free midrange irradiation analysis regions, depending on the material system. Lastly, analysis of amorphization/precipitation require even higher energies (>10 MeV).
07 ISOTOPE AND RADIATION SOURCES↗
Change in equilibrium position of misfit dislocations at the GaN/sapphire interface by Si-ion implantation into sapphire—I. Microstructural characterization
Much research has been done to reduce dislocation densities for the growth of GaN on sapphire, but has paid little attention to the elastic behavior at the GaN/sapphire interface. In this study, we have examined effects of the addition of Si to a sapphire substrate on its elastic property and on the growth of GaN deposit. Si atoms are added to a c-plane sapphire substrate by ion implantation. The ion implantation results in scratches on the surface, and concomitantly, inhomogeneous distribution of Si. The scratch regions contain a higher concentration of Si than other regions of the sapphire substrate surface, high-temperature GaN being poorly grown there. However, high-temperature GaN is normally grown in the other regions. The GaN overlayer in the normally-grown regions is observed to have a lower TD density than the deposit on the bare sapphire substrate (with no Si accommodated). As compared with the film on an untreated, bare sapphire, the cathodoluminescence defect density decreases by 60 % for the GaN layer normally deposited on the Si-ion implanted sapphire. As confirmed by a strain mapping technique by transmission electron microscopy (geometric phase analysis), the addition of Si in the normally deposited regions forms a surface layer in the sapphire elastically more compliant than the GaN overlayer. The results suggest that the layer can largely absorb the misfit strain at the interface, which produces the overlayer with a lower defect density. Our results highlight a direct correlation between threading-dislocation density in GaN deposits and the elastic behavior at the GaN/sapphire interface, opening up a new pathway to reduce threading-dislocation density in GaN deposits.
36 MATERIALS SCIENCE↗
Ion Implanted Passivated Contacts for Interdigitated Back Contacted Solar Cells
We describe work towards an interdigitated back contacted (IBC) solar cell utilizing ion implanted, passivated contacts. Formation of electron and hole passivated contacts to n-type CZ wafers using tunneling SiO2 and ion implanted amorphous silicon (a-Si) are described. P and B were ion implanted into intrinsic amorphous Si films at several doses and energies. A series of post-implant anneals showed that the passivation quality improved with increasing annealing temperatures up to 900 degrees C. The recombination parameter, Jo, as measured by a Sinton lifetime tester, was Jo ~ 14 fA/cm2 for Si:P, and Jo ~ 56 fA/cm2 for Si:B contacts. The contact resistivity for the passivated contacts, as measured by TLM patterns, was 14 milliohm-cm2 for the n-type contact and 0.6 milliohm-cm2 for the p-type contact. These Jo and pcontact values are encouraging for forming IBC cells using ion implantation to spatially define dopants.
14 SOLAR ENERGY↗
Adroit Materials Final Scientific/Technical Report kV-class GaN-based Junction Barrier Schottky diodes using ion implantation
The primary aim of this research was to develop GaN-based Junction Barrier Schottky (JBS) diodes using an innovative ion implantation process previously established in ARPA-E funded projects. The central focus of our proposed technology revolves around selective area p-type doping, accomplished through the implantation of Mg ions. This approach builds upon our successes in the ARPA-E PNDIODES program, advancing towards commercial device integration. Selective area p-doping plays a pivotal role in realizing the next generation of GaN-based power devices, capable of significantly reducing the carbon footprint in the United States by several million tons. While ion implantation is a well-established technique for achieving selective area doping in SiC and Si materials, its feasibility in GaN had not been demonstrated until now. To fabricate high voltage GaN JBS diodes, we initially created thick n-type drift layers with high carrier concentrations ranging from 5×1015 cm-3 to 2×1016 cm-3 and very high mobilities. Subsequently, Mg ions were selectively implanted to form p-type islands within the n-type drift layer. To reduce electric field crowding at the edge of the diode and to achieve high breakdown voltage, junction edge termination (JTE) and floating field rings (FFRs) were formed using Mg implantation. A high temperature, high-pressure post-implantation annealing process was carried out to activate the implanted Mg ions. As a result, we were able to demonstrate GaN JBS diodes with a breakdown voltage of 915 V and an on-resistance of 0.6 mΩ·cm2. These diodes exhibited a forward bias current density of 1 kA/cm2 at 1.5 V. Subsequently, we achieved GaN JBS diodes with a remarkable breakdown voltage of 1900 V and an on-resistance of 1.9 mΩ·cm2, capable of sustaining a forward bias current density of 0.5 kA/cm2 at 1.5 V. Importantly, the ON and OFF state performance of these GaN JBS diodes surpassed that of Si and SiC-based power diodes reported in existing literature. Lastly, we successfully grew 60 μm thick GaN:Si layers using HVPE with a carrier concentration of approximately 3 to 5×1015 cm-3. Based on simulation and empirical data these devices represent 5 kV GaN JBS power diodes, leveraging the developed processes in this project.
36 MATERIALS SCIENCE↗
Computational stochastic model of ions implantation
Implantation flux ions into crystal leads to phase transition /PT/ 1-st kind. Damaging lattice is associated with processes clustering vacancies and gaseous bubbles as well their brownian motion. System of stochastic differential equations /SDEs/ Ito for evolution stochastic dynamical variables corresponds to the superposition Wiener processes. The kinetic equations in partial derivatives /KE/, Kolmogorov-Feller and Einstein-Smolukhovskii, were formulated for nucleation into lattice of weakly soluble gases. According theory, coefficients of stochastic and kinetic equations uniquely related. Radiation stimulated phase transition are characterized by kinetic distribution functions /DFs/ of implanted clusters versus their sizes and depth of gas penetration into lattice. Macroscopic parameters of kinetics such as the porosity and stress calculated in thin layers metal/dielectric due to Xe{sup ++} irradiation are attracted as example. Predictions of porosity, important for validation accumulation stresses in surfaces, can be applied at restoring of objects the cultural heritage.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Generation of Tin-Vacancy Centers in Diamond via Shallow Ion Implantation and Subsequent Diamond Overgrowth
Group IV color centers in diamond have garnered great interest for their potential as optically active solid-state spin qubits. The future utilization of such emitters requires the development of precise site-controlled emitter generation techniques that are compatible with high-quality nanophotonic devices. This task is more challenging for color centers with large group IV impurity atoms, which are otherwise promising because of their predicted long spin coherence times without a dilution refrigerator. For example, when applied to the negatively charged tin-vacancy (SnV – ) center, conventional site-controlled color center generation methods either damage the diamond surface or yield bulk spectra with unexplained features. Here we demonstrate a novel method to generate site-controlled SnV – centers with clean bulk spectra. We shallowly implant Sn ions through a thin implantation mask and subsequently grow a layer of diamond via chemical vapor deposition. This method can be extended to other color centers and integrated with quantum nanophotonic device fabrication.
36 MATERIALS SCIENCE↗
Defect Formation under Nitrogen-Ion Implantation and Subsequent Annealing in GaAs Structures with an Uncovered Surface and a Surface Covered with an AlN Film
The concentration profiles of defects produced in structures upon the implantation of nitrogen ions into GaAs epitaxial layers with an uncovered surface and that covered with an AlN film and subsequent annealing are studied. The ion energies and the implantation doses are chosen so that the nitrogen-atom concentration profiles coincided in structures of both types. Rutherford proton backscattering spectra are measured in the random and channeling modes, and the concentration profiles of point defects formed are calculated for the samples under study. It is found that the implantation of nitrogen ions introduces nearly the same number of point defects into structures of both types, and the formation of an AlN film by ion-plasma sputtering is accompanied by the formation of an additional number of defects. However, the annealing of structures of both types leads to nearly the same concentrations of residual defects.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Design and application of ion-implanted polySi passivating contacts for interdigitated back contact c-Si solar cells
Ion-implanted passivating contacts based on poly-crystalline silicon (polySi) are enabled by tunneling oxide, optimized, and used to fabricate interdigitated back contact (IBC) solar cells. Both n-type (phosphorous doped) and p-type (boron doped) passivating contacts are fabricated by ion-implantation of intrinsic polySi layers deposited via low-pressure chemical vapor deposition and subsequently annealed. The impact of doping profile on the passivation quality of the polySi doped contacts is studied for both polarities. It was found that an excellent surface passivation could be obtained by confining as much as possible the implanted-and-activated dopants within the polySi layers. The doping profile in the polySi was controlled by modifying the polySi thickness, the energy and dose of ion-implantation, and the temperature and time of annealing. An implied open-circuit voltage of 721 mV for n-type and 692 mV for p-type passivating contacts was achieved. Besides the high passivating quality, the developed passivating contacts exhibit reasonable high conductivity (R{sub sh n-type} = 95 Ω/□ and R{sub sh p-type} = 120 Ω/□). An efficiency of 19.2% (V{sub oc} = 673 mV, J{sub sc} = 38.0 mA/cm{sup 2}, FF = 75.2%, and pseudo-FF = 83.2%) was achieved on a front-textured IBC solar cell with polySi passivating contacts as both back surface field and emitter. By improving the front-side passivation, a V{sub OC} of 696 mV was also measured.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗