Surface damage and topography of erbium metal films implanted with helium to high fluences

Topographical and expansion effects which occur as a result of implanting erbium thin films with helium up to fluences of 1.5 × 10¹⁸ He⁺/cm² are described. There exists an inverse relationship between critical dose and annealing temperature with respect to the formation of surface bubbles. Post implantation annealing at or below 400°C is found to strongly reduce implantation induced expansion for doses less than 3.5 × 10¹⁷ He⁺/cm², but is observed to result in increased expansion above this dose. At temperatures above 400°C, expansion is increased for all doses investigated. Details of bubble development in the implanted layer are discussed and the manner in which surface bubbles develop from enlarged subsurface bubbles is illustrated.     

Structural state of III nitride layers implanted with erbium ions

The defect structure of AlGaN/GaN superlattices and GaN layers grown through vapor-phase epitaxy from organometallic compounds is investigated using x-ray diffraction analysis before and after implantation with erbium ions at an energy of 1 MeV and a dose of 3 × 10¹⁵ cm^?2, as well as after annealing. For a superlattice with a total thickness larger than the implantation depth, the satellites of the superlattice region strained under the action of ions disappear in the x-ray diffraction pattern after annealing at temperatures higher than 900°C. This suggests that the radiation-induced defects responsible for the positive deformation in the layer are annealed at these temperatures. However, annealing even at a temperature of 1050°C does not lead to complete recovery of the initial state and the positive deformation in the remaining regions is caused by residual defects. An analysis of the x-ray diffraction patterns demonstrates that, in samples with thin superlattices located at the depth corresponding to maximum radiation damage, the periodic structure that disappears after implantation at a dose of 3 × 10¹⁵ cm^?2 is not recovered even after annealing at a temperature of 1050°C. This inference is confirmed by the results of examinations with an electron microscope.     

Upconversion luminescence from Er-N codoped of ZnO nanowires prepared by ion implantation method

Nitrogen and erbium co-doped of ZnO nanowires (NWs) are fabricated by ion implantation and subsequent annealing in air. The incorporation of Er³⁺ and N⁺ ions is verified by energy dispersive X-ray spectroscopy (EDS) and Raman spectra. The samples exhibit upconversion photoluminescence around ∼550 nm and ∼660 nm under an excitation at 980 nm. It is discovered that the N-doped can drastically increase the upconversion photoluminescence intensity by modifying the local structure around Er³⁺ in ZnO matrix. The enhancement of the PL intensity by the N-doped is caused by the formation of ErO_6−xN_x octahedron complexes. With the increase of the annealing temperature (T_a), the Er³⁺ ions diffuse towards the surface of the NWs, which benefits the red emission and evokes the variation of intensity ratio owing to the existence of some organic groups.     

Influence of the ion synthesis and ion doping regimes on the effect of sensitization of erbium emission by silicon nanoclusters in silicon dioxide films

The photoluminescence spectra of erbium centers in SiO₂ films with ion-synthesized silicon nanoclusters under nonresonant excitation were investigated. Erbium was introduced into thermal SiO₂ films by ion implantation. The dependences of photoluminescence intensity on the dose, the order of ion implantation of Si and Er, the annealing temperature, and additional Ar⁺ and P⁺ ion irradiation regimes, i.e., factors determining the influence of radiation damage and doping on sensitization of erbium luminescence by silicon nanoclusters, were determined. It was found that the sensitization effect and its amplification due to doping with phosphorus are most pronounced under the conditions where nanoclusters are amorphous. The quenching of photoluminescence due to radiation damage in this case manifests itself to a lesser extent than for crystalline nanoclusters. The role of various factors in the observed regularities was discussed in the framework of the existing concepts of the mechanisms of light emission and energy exchange in the system of silicon nanoclusters and erbium centers.     

Nitrogen centers in GaP produced by hot implantation

Backscattering yields of 1.5 MeV?He⁺ ions and low temperature photoluminescence (PL) spectra were measured in GaP crystals implanted with 200 keV?N⁺ ions as functions of ion-dose, temperature during implantation and annealing temperature after implantation. Backscattering results indicate that hot implantation at 500°C greatly reduces radiation damage. The PL intensities of NN lines become maximum in the sample implanted with N⁺ ions of 3 × 10¹⁴cm^?2 at 500°C, and annealed at 1000°C for 1 hr with aluminum glass. The PL intensity is comparable to that of the nitrogen-doped sample during liquid phase epitaxy which is widely accepted as the best method of introducing nitrogen into GaP crystals. In the case of 500°C—hot implantation, the radiation damage produced during implantation is annealed out at 700 ~ 800°C and the implanted nitrogen substitutes for the phosphorous sites after annealing at 900 ~ 1000°C. Some kinds of defects or strains remain around the NN centers even in implanted samples with a maximum PL efficiency. These defects or strains don't seem to reduce the PL efficiency. In the case of room temperature implantation, PL efficiency decreases to one-hundredth or one-thousandth due to the formation of the non-crystalline state compared with hot implantation.     

Nitrogen implantation in GaAs1−xPx (x=0.4; 0.65)

Nitrogen ions were implanted in GaAs_1−xP_x (x=0.4; 0.65) at room temperature at various doses from 5×10¹² cm⁻² to 5×10¹⁵ cm⁻² and annealed at temperatures from 600°C up to 950°C using a sputtered SiO₂ encapsulation to investigate the possibility of creating isoelectronic traps by ion implantation. Photoluminescence and channeling measurements were performed to characterize implanted layers. The effects of damage induced by optically inactive neon ion implantation on photoluminescence spectrum were also investigated. By channeling measurements it was found that damage induced by nitrogen implantation is removed by annealing at 800°C. A nitrogen induced emission intensity comparable to the intensity of band gap emission for unimplanted material was observed for implanted GaAs_0.6P_0.4 after annealing at 850°C, while an enhancement of the emission intensity by a factor of 180 as compared with an unimplanted material was observed for implanted GaAs_0.35P_0.65 after annealing at 950°C. An anomalous diffusion of nitrogen atoms was found for implanted GaAs_0.6P_0.4 after annealing at and above 900°C.     

Formation of nanoparticles containing zinc in Si(001) by ion-beam implantation and subsequent annealing

The formation of nanoparticles containing zinc in Si(001) substrates by the implantation of ⁶⁴Zn⁺ ions and subsequent annealing in dry oxygen at 800 and 1000°C for 1 h is studied. The structure of the samples is studied by high-resolution transmission electron microscopy, X-ray diffraction, and photoluminescence spectroscopy. 20-nm zinc nanoparticles located at a depth of about 50 nm are revealed in the as-implanted sample. 10–20-nm pores are observed in the surface layer. Annealing leads to oxidation of the Zn nanoparticles to the Zn₂SiO₄ state. It is shown that the oxidation of Zn nanoparticles begins on their surface and at an annealing temperature of 800°C results in the formation of nanoparticles with the “соre–shell” structure. The X-ray diffraction technique shows simultaneously two Zn and Zn₂SiO₄ phases. ZnO nanoparticles are not formed under the given implantation and annealing conditions.     

Photoluminescence and structural defects in silicon layers implanted by iron ions

The photoluminescence spectra of silicon samples implanted by ⁵⁶Fe⁺ ions [energy, 170 keV; dose, 1×10¹⁶, (2–4)×10¹⁷ cm^?2] and annealed at temperatures of 800, 900, and 1000°C are measured. The structure of the samples at each stage of treatment is investigated using transmission electron microscopy (TEM). It is found that the phase formation and morphology of crystalline iron disilicide precipitates depend on the dose of iron ions and the annealing temperature. A comparison of the dependences of the intensity and spectral distribution of the photoluminescence on the measurement temperature, annealing temperature, and morphology of the FeSi₂ phase revealed the dislocation nature of photoluminescence.     

Properties of erbium silicate doped with chromium in porous silicon

The possible formation of chromium-doped erbium silicate Er₂SiO₅: Cr in thin layers of porous silicon is demonstrated. This paper reports on studies of the photoluminescence, electron paramagnetic resonance, and transverse current transport in porous silicon layers (with different chromium and erbium contents) grown on n-and p-silicon single crystals heavily doped with shallow impurities. The Er₂SiO₅: Cr phase with the photoluminescence maxima at approximately 1.3 and 1.5 μm manifests itself after high-temperature annealing at 1000°C. The introduction of erbium and annealing at 700°C increase the intensity of the red photoluminescence of porous silicon by several factors. The decrease in the electrical conductivity of porous silicon suggests the onset of the formation of erbium silicate. The current-voltage characteristics exhibit a nonlinear behavior with an exponential dependence of the current on the voltage due to the discrete electron tunneling. An electron paramagnetic resonance spectrum of P _b centers in p-type heavily doped silicon is observed for the first time.     

Ti离子注入和退火对ZnS薄膜结构和光学性质的影响

利用真空蒸发法在石英玻璃衬底上制备了ZnS薄膜,将能量80 keV,剂量1×10¹⁷ cm^-2的Ti离子注入到薄膜中,并将注入后的ZnS薄膜进行退火处理,退火温度500—700 ℃.利用X射线衍射（XRD）研究了薄膜结构的变化,利用光致发光（PL）和光吸收研究了薄膜光学性质的变化.XRD结果显示,衍射峰在500 ℃退火1 h后有一定程度的恢复;光吸收结果显示,离子注入后光吸收增强,随着退火温度的上升,光吸收逐渐降低,吸收边随着退火温度的提高发生蓝移;PL显示,薄 关键词： ZnS薄膜 离子注入 X射线衍射 光致发光     

Annealing of γ-ray irradiated lithium compensated p-type silicon

Abstract

Annealing behavior of electrical properties and photoluminescence spectra both at 77 °K in electron-irradiated melt-grown n-GaAs were investigated. Defects electrically active in the Hall mobility and carrier removal anneal through two stages centered at 250° and 460 °K. From the temperature dependence of carrier concentration the existence of a defect level located near 0.15 eV below the conduction band is supposed. Several emission bands are resolved at 1.51, 1.47, 1.415, 1.305 and ～1.2 eV in photoluminescence experiments. Electron irradiation (1.5–2.0 MeV) causes a remarkable decrease in emission intensity of 1.51 and ～1.2 eV bands. Recovery of emission intensity occurs remarkably when samples are annealed to 520 °K which would correspond to the 460 °K annealing stage for carrier concentration and Hall mobility. The 250 °K annealing stage is not observed in photoluminescence experiments. The 1.415 eV peak appears clearly after irradiation and grows remarkably with the 520 °K annealing, especially in Si-doped samples, resulting in large reverse annealing. This band is tentatively speculated to be a complex of Si on As site with As vacancy. Moreover, in samples doped with Te a new emission band at 1.305 eV (9500 Å) is observed after 470°–620 °K annealing.     

Optical properties of ZnO and Al2O3 implanted with silver ions

ZnO and Al₂O₃ samples implanted with 30-keV silver ions with fluences in the interval (0.25–1.00) × 10¹⁷ ions/cm² are studied by the method of optical photometry in the visible part of the spectrum. The optical transmission spectra of the implanted samples exhibit a selective band associated with surface plasmon resonance absorption of silver nanoparticles. The intensity of this band nonmonotonically depends on the implantation fluence. The silver ion depth distribution in the samples is calculated. It is shown that the non-monotonicity observed in experiments is due to an increase in the substrate sputtering ratio with increasing implantation fluence. It is found that vacuum thermal annealing of the implanted Al₂O₃ layers up to 700°C causes a considerable narrowing of the plasmon absorption bandwidth without a tangible change in its intensity. At higher annealing temperatures, the plasmon absorption band broadens and its intensity drops. Annealing of the ZnO films under such conditions causes their complete vaporization.     

Photoluminescence study of Ce-doped silica films

Ce-doped silica films with different Ce concentrations were prepared by ion-beam sputtering and ion implantation. The films containing 1.2 at% Ce were annealed at temperatures from 500 °C to 1200 °C in air ambient, and were annealed in different ambient at 1100 °C. Ce-related photoluminescence was observed in films sensitive to the Ce concentrations, annealing temperatures and the annealing ambient. The peak intensity of the photoluminescence band is approximately linear with Ce concentrations. Also, the photoluminescence intensity is dependent on the annealing temperatures and reaches its highest value after annealing at 700 °C. In addition, the experimental results show that compared with the annealing in an air ambient, the photoluminescence intensity can be enhanced with nitrogen gas. There would be no obvious change for the photoluminescence position or shape.     

Positron annihilation study of voids in a neutron irradiated aluminum single crystal

We have measured the lifetimes of positrons in an aluminum single crystal which was irradiated to a fast neutron fluence of 1.5·10²¹ n/cm² (>0.18 MeV) at 50°C. These irradiation conditions produced 4.2·10¹⁴ voids/cm³ with a mean diameter of 330 Å, as determined by both small-angle x-ray scattering and transmission electron microscopy. The positron lifetime spectra were resolved into three lifetime components of 100, 300, and 500 ps. The short lifetime component is a result of fast trapping of positrons by the voids; the long lifetime components result from annihilations within the voids. The intensity of the long lifetime components increases with temperature in the range 80 to 300 K and supports the model of a positron state at the void surface. The positron diffusion coefficient appears to have aT ^1/2-dependence. A magnetic quenching experiment shows no indication of positronium formation. Finally, an isochronal heat treating sequence shows that the voids anneal out between 200 and 300°C, and that the lifetime spectrum after annealing is described by a single component of 170 ps, the observed lifetime in unirradiated aluminum.     

Effect of implantation temperature on the blistering behavior of hydrogen implanted GaN

GaN epitaxial layers were implanted by 100 keV H⁺ ions at different implantation temperatures (LN₂, RT and 300 °C) with a fluence of 2.5×10¹⁷ cm^?2. The implanted samples were characterized using Nomarski optical microscopy, AFM, XRD, and TEM. Topographical investigations of the implanted surface revealed the formation of surface blistering in the as-implanted samples at 300 °C and after annealing at higher temperature for the implantation at LN₂ and RT. The physical dimensions of the surface blisters/craters were dependent on the implantation temperature. XRD showed the dependence of damage-induced stress on the implantation temperature with higher stress for the implantation at 300 °C. TEM investigations revealed the formation of a damage band in all the cases. The damage band was filled with large area microcracks for the implantation at 300 °C, which were responsible for the as-implanted surface blistering.     

Influence of Cr<Superscript>+</Superscript> ion implantation and pulsed ion-beam annealing on the formation and optical properties of Si/CrSi<Subscript>2</Subscript>/Si(111) heterostructures

The effect of pulsed ion-beam annealing on the surface morphology, structure, and composition of single-crystal Si(111) wafers implanted by chromium ions with a dose varying from 6 × 10¹⁵ to 6 × 10¹⁶ cm⁻² and on subsequent growth of silicon is investigated for the first time. It is found that pulsed ion-beam annealing causes chromium atom redistribution in the surface layer of the silicon and precipitation of the polycrystalline chromium disilicide (CrSi₂) phase. It is shown that the ultrahigh-vacuum cleaning of the silicon wafers at 850°C upon implantation and pulsed ion-beam annealing provides an atomically clean surface with a developed relief. The growth of silicon by molecular beam epitaxy generates oriented 3D silicon islands, which coalesce at a layer thickness of 100 nm and an implantation dose of 10¹⁶ cm⁻². At higher implantation doses, the silicon layer grows polycrystalline. As follows from Raman scattering data and optical reflectance spectroscopy data, semiconducting CrSi₂ precipitates arise inside the silicon substrate, which diffuse toward its surface during growth.     

Hot electron studies of lattice damage created in silicon by implantation of 2.8 MeV protons

Abstract

In this paper we report the results of a study of the annealing properties of the ionized defect density associated with the damage created in the silicon lattice by implantation of 2.8 MeV protons at room temperature. In particular, the annealing of damage created by implanting to a level of 4.43 × 10¹² protons/cm² is reported. The resulting isochronal annealing curve covered the temperature range from 70°C to 460°C. Two major annealing stages are discussed, one a broad stage between 70°C to 200°C and the other an abrupt annealing stage between 440°C to 460°C. Between the temperature range 200°C to 440°C the number of ionized defects remained relatively constant. Above 460°C no detectable effects of the proton implantation remained.     

Annealing effects on the microstructure of sputtered gold layers on oxidized silicon investigated by scanning electron microscopy and scanning probe microscopy

The structure of Au layers deposited by sputtering on oxidized p-type Si(100) substrates is investigated by a combination of scanning electron microscopy and scanning probe microscopy. The effect of the temperature on the grain structure of the layers has been determined, revealing that an annealing temperature of 300° C results in a larger grain size and smoother surfaces but generates some cracks in the film surface. At an annealing temperature of 500° C, further grain growth is observed, but a high density of cracks and voids also results while there is little enhancement regarding the smoothness of the grain surfaces.     

Positron annihilation study of voids in a neutron irradiated aluminum single crystal

We have measured the lifetimes of positrons in an aluminum single crystal which was irradiated to a fast neutron fluence of 1.5·10²¹ n/cm² (>0.18 MeV) at 50°C. These irradiation conditions produced 4.2·10¹⁴ voids/cm³ with a mean diameter of 330 ?, as determined by both small-angle x-ray scattering and transmission electron microscopy. The positron lifetime spectra were resolved into three lifetime components of 100, 300, and 500 ps. The short lifetime component is a result of fast trapping of positrons by the voids; the long lifetime components result from annihilations within the voids. The intensity of the long lifetime components increases with temperature in the range 80 to 300 K and supports the model of a positron state at the void surface. The positron diffusion coefficient appears to have aT ^1/2-dependence. A magnetic quenching experiment shows no indication of positronium formation. Finally, an isochronal heat treating sequence shows that the voids anneal out between 200 and 300°C, and that the lifetime spectrum after annealing is described by a single component of 170 ps, the observed lifetime in unirradiated aluminum. Research sponsored in part by the U.S.Atomic Energy Commission under contract with the Union Carbide Corporation.     

Photoluminescence in germanium with a quasi-equilibrium dislocation structure

The dislocation-related photoluminescence of n-Ge single crystals with a quasi-equilibrium structure of 60° dislocations is investigated at a temperature of 4.2 K. It is shown that the dislocation-related photoluminescence spectra are described by a set involving from 8 to 13 Gaussian lines with a width of less than 15 meV. With due regard for the data available in the literature, the Gaussian lines with maxima at energies in the range 0.47 < E _m ≤ 0.55 eV are assigned to the emission of 90° Shockley partial dislocations involved in quasiequilibrium segments of 60° dislocations with different values of the stacking fault width Δ (Δ = Δ₀, Δ < Δ₀, and Δ > Δ₀). It is revealed that the d8 line at the energy E _m = 0.513 eV, which corresponds to the emission of straight segments with the equilibrium stacking fault width Δ₀, dominates in the photoluminescence spectra only at dislocation densities N _D < 10⁶ cm^?2. As the dislocation density N _D increases, the intensity of the d8 line decreases with the d7 line (E _m ≈ 0.507 eV) initially and the d7 and d6 lines (E _m ≈ 0.501 eV) then becoming dominant in the photoluminescence spectrum. The d7 and d6 lines are attributed to the emission of segments with stacking fault widths Δ < Δ₀. Possible factors responsible for the formation of stacking faults with particular widths Δ ≠ Δ₀ for quasi-equilibrium dislocations are discussed.