Implantation-induced Lattice Damage Research Articles

Photoluminescence properties and DFT simulations of the Cr ion-implanted (100)-oriented β-Ga2O3 single crystals

Beta-gallium oxide (β-Ga2O3) with tunable optical and electrical properties has great potential in power metal-semiconductor devices. In this work, (100)-oriented β-Ga2O3 single crystals were implanted with 190 keV Cr ions at different fluencies, and their photoluminescence, band structures, and electronic properties have been studied in detail. Our results clearly show that ion implantation-induced lattice damage could be recovered and the implanted Cr ions in (100)-oriented β-Ga2O3 can be activated to produce NIR (R-lines and broadband) emissions after the post-implantation annealing at 900 °C. Temperature-dependent photoluminescence (TDPL) measurements indicate that the increasing temperature could lead to weakness and redshifts of the R-lines emissions centered at about 692 nm, while the broadband emission centered at about 713 nm enhanced because of a higher thermal occupation at the 4T2 state than at the 2E state. Results from Density functional theory (DFT) calculations demonstrate that the Ga atom’s replacements with Cr atoms could occur at the tetrahedral or octahedral sites of the lattices, which allows the Cr atoms to be activated to act as the NIR emission centers.

Lattice damage and helium bubbles formation in KTaO3 crystals induced by helium ion implantation

Potassium tantalite (KTaO[Formula: see text] has shown an excellent performance in optoelectronic applications, proving its advantages with respect to fabricating single crystal thin films by ion implantation. This work introduces the damage formation of KTaO3 under 200 keV He ion implantation at room temperature and He bubbles accumulation. Ion implantation-induced lattice damage before and after annealing was quantitatively analyzed by using the Rutherford backscattering spectrometry in channeling technique. The crystals phase analysis of the samples under different fluences was studied by using the X-ray diffraction technique. For 200 keV He ions, the accumulation and migration of He bubbles were induced by the thermal annealing effect under high fluences of He[Formula: see text]. The He bubbles appear obviously coarsening and embrittlement with thermal annealing. The blistering phenomenon caused by He ion implantation is the physical basis for the smart-cut technique, which allows the preparation of high-quality single-crystal films.

Observation of enhanced infrared absorption in silicon supersaturated with gold by pulsed laser melting of nanometer-thick gold films

We demonstrate that pulsed laser melting (PLM) of thin 1, 5, and 10 nm-thick vapor-deposited gold layers on silicon enhances its room-temperature sub-band gap infrared absorption, as in the case of ion-implanted and PLM-treated silicon. The former approach offers reduced fabrication complexity and avoids implantation-induced lattice damage compared to ion implantation and pulsed laser melting, while exhibiting comparable optical absorptance. We additionally observed strong broadband absorptance enhancement in PLM samples made using 5- and 10-nm-thick gold layers. Raman spectroscopy and Rutherford backscattering analysis indicate that such an enhancement could be explained by absorption by a metastable, disordered and gold-rich surface layer. The sheet resistance and the diode electrical characteristics further elucidate the role of gold-supersaturation in silicon, revealing the promise for future silicon-based infrared device applications.

Study of surface exfoliation on 6H-SiC induced by H2+ implantation

The effect of lattice damage generated by the H2+-implantation on exfoliation efficiency in 6H-SiC wafers is investigated. <0001> 6H-SiC wafers were implanted with 134keVH2+ ions to ion fluences from 1.5×1016 to 5×1016 H2+ cm−2 and subsequently annealed at temperatures from 973K to 1373K. The samples were studied by a combination of optical microscopy and transmission electron microscopy. Only after 1373K annealing for 15min, blisters and exfoliation occur on the H2+-implanted sample surface. With increasing the implantation fluences from 1.5×1016 to 3.75×1016 H2+ cm−2, the exfoliation mean size decreases, while the exfoliation density increases. For the highest fluence of 5×1016 H2+ cm−2, seldom exfoliations occur on the sample surface. Microstructure analysis shows that exfoliation efficiency is largely controlled by the H2+-implantation-induced lattice damage. The depth of the microcrack is related to the implantation fluence. The effect of implantation fluence on dislocation loops, platelet nucleation and growth is investigated.

Interactions of hydrogen with vanadium in crystalline silicon

In this work, we have investigated interactions of vanadium with hydrogen in n‐ and p‐type float zone grown silicon using deep level transient spectroscopy (DLTS), Laplace DLTS, capacitance‐voltage and secondary ion mass spectroscopy measurements (SIMS). Vanadium was introduced into Si wafers by ion implantation with subsequent heat treatments at 800 °C for removing the implantation induced lattice damage. In the DLTS spectra of the annealed samples, we have observed two deep level states due to interstitial vanadium (Vi) atoms in n‐type Si and one in p‐type Si. A comparison of concentration profiles of the Vi atoms with those for the total concentration of V measured by SIMS has shown that at the projected implantation depth the [Vi]/[Vtotal] ratio is less than 0.05 at chemical concentration of vanadium of 1 × 1015 cm−3, so the majority of V atoms are in electrically inactive states in this region. At lower chemical concentrations of vanadium, similar values of [Vi] and [Vtotal] are observed. After the treatment of the n‐type V‐doped samples in a remote hydrogen plasma at room temperature, we have found that the concentration of the Vi atoms decreases while additional electron traps emerge in the DLTS spectra. A trap with the highest concentration has been attributed to a vanadium–hydrogen complex. In the p‐type Si:V samples, no new levels have emerged in the DLTS spectra after the H‐plasma treatments. It is suggested that in p‐type Si:V an interaction of H atoms with the Vi atoms is suppressed because of the Coulombic repulsion of positively charged Vi and hydrogen defects. It is argued that no electrically active defects are formed in either the n‐ or p‐type Si:V samples due to possible interactions of hydrogen with electrically inactive V‐related defects. We present evidence that annealing of the n‐type Si:V samples in the temperature range 75–125 °C following the application of hydrogen plasma results in up to 20% decrease in the total concentration of electrically active V‐related defects, indicating the formation of some electrically inactive V–H complexes. Heat treatments at temperatures above 175 °C have resulted in the disappearance of all the V–H complexes and recovery of electrical activity of the Vi atoms.

CEMS study of defect annealing in Fe implanted AlN

An AlN thin film grown on sapphire substrate was implanted with 45 keV 57Fe and 56Fe ions at several energies to achieve a homogeneous concentration profile of approximately 2.6 at.%. in the AlN film. Conversion electron Mossbauer Spectroscopy data were collected after annealing the sample up to 900 °C. The spectra were fitted with three components, a single line attributed to small Fe clusters, and two quadrupole split doublets attributed to Fe substituting Al in the wurtzite AlN lattice and to Fe located in implantation induced lattice damage. The damage component shows significant decrease on annealing up to 900 °C, accompanied by corresponding increases in the singlet component and the substitutional Fe.

Ion implantation induced blistering of rutile single crystals

The rutile single crystals were implanted by 200keV He+ ions with a series fluence and annealed at different temperatures to investigate the blistering behavior. The Rutherford backscattering spectrometry, optical microscope and X-ray diffraction were employed to characterize the implantation induced lattice damage and blistering. It was found that the blistering on rutile surface region can be realized by He+ ion implantation with appropriate fluence and the following thermal annealing.

Depth Profiling of Electronic Transport Parameters in n-on-p Boron-Ion-Implanted Vacancy-Doped HgCdTe

We report results of a detailed study of electronic transport in n-on-p junctions formed by 150-keV boron-ion implantation in vacancy-doped p-type Hg0.769Cd0.231Te without postimplantation thermal annealing. A mobility spectrum analysis methodology in conjunction with a wet chemical etching-based surface removal approach has been employed to depth profile the transport characteristics of the samples. In the as-implanted samples, three distinct electron species were detected which are shown to be associated with (a) low-mobility electrons in the top 220-nm surface-damaged layer (E1: μ80K = 2940 cm2/Vs), (b) the B-ion implantation region in the top 500-nm region (E2: μ80K = 7490 cm2/Vs), and (c) high-mobility electrons in the n-to-p transition region at a depth of 600 nm to 700 nm (E3: μ80K = 25,640 cm2/Vs). Due to the maximum magnetic field employed (2 T), hole carriers from the underlying vacancy-doped p-type region were detected only after the removal of the top 220 nm of the profiled sample (μ80K = 126 cm2/Vs), revealing fully p-type character 800 nm below the original sample surface. A comparison of the extracted E2 electron concentration and calculated B-impurity profile suggests that the n-type region is due primarily to near-surface implantation-induced lattice damage.

Effect of Cr implantation on structural and optical properties of AlN thin films

Molecular beam epitaxy (MBE) grown AlN thin layer on sapphire substrates have been implanted with Cr+ ions for various dose from 1013 to 1015 cm−2. The analyses were carried out by an X-ray diffractometer (XRD), Raman spectroscopy, a spectrophotometer and spectroscopic ellipsometry (SE) for structural and optical analyses. E2(high) and A1(LO) Raman modes of AlN layer have been observed and analyzed. The behavior of Raman shift and the variation in intensity and in peak width of Raman modes as a function of ions flux are explained on the basis of chromium substituting aluminum atom and implantation-induced lattice damage. Both Raman and X-ray analyses reveal that the incorporation of chromium atoms increases in the host lattice with the increasing of Cr ions fluence. The band gap energy was determined by using transmission spectra. It was found that the band gap energy decreases as the ion dose increases. The band gap of the unimplanted AlN is 6.02 eV and it decreases down to 5.92 eV for the Cr+-implanted AlN with a ion dose of 1×1015 cm−2. Optical properties such as optical constants of the samples were examined by using a spectroscopic ellipsometer. It was observed that the refractive index (n) decreases with the increasing of ion dose.

Raman scattering studies on manganese ion-implanted GaN

This paper reports that the Raman spectra have been recorded on the metal-organic chemical vapour deposition epitaxially grown GaN before and after the Mn ions implanted. Several Raman defect modes have emerged from the implanted samples. The structures around 182 cm−1 modes are attributed to the disorder-activated Raman scattering, whereas the 361 cm−1 and 660 cm−1 peaks are assigned to nitrogen vacancy-related defect scattering. One additional peak at 280 cm−1 is attributed to the vibrational mode of gallium vacancy-related defects and/or to disorder activated Raman scattering. A Raman-scattering study of lattice recovery is also presented by rapid thermal annealing at different temperatures between 700 °C and 1050 °C on Mn implanted GaN epilayers. The behaviour of peak-shape change and full width at half maximum (FWHM) of the A1(LO) (733 cm−1) and EH2 (566 cm−1) Raman modes are explained on the basis of implantation-induced lattice damage in GaN epilayers.

X-ray absorption fine structure study of In implanted GaN: Effect of annealing

GaN implanted with 700 keV In ions with fluence 5 × 10 15 cm −2 is studied using X-ray absorption fine structure (XAFS) spectroscopies at the N and Ga K edges. Rutherford backscattering (RBS) reveals that implantation renders the top 200 nm of the GaN film amorphous while the underlying 250 nm of the film are highly defective. The increase of the static disorder due to the implantation induced lattice damage is evident both in the N K edge NEXAFS and the Ga K edge EXAFS spectra. Indium implantation also induces the formation of N 2 evinced by the evolution of a sharp resonance line (RL) that corresponds to 1s → π * transitions of molecular nitrogen. The N 2 molecules dissociate after annealing at temperatures higher than 800 °C. The bonding environment of Ga is also affected by the implantation and annealing: a marginal increase of the Ga–Ga distance is observed due to the incorporation of In atoms and/or formation of defects. The coordination number of the second nearest neighboring (NN) shell is reduced by more than 50% after the implantation but recovers after annealing at 800 °C. Further increase of the annealing temperature causes nitrogen loss as it is deduced by the reduction of the coordination number in the first NN shell by about 20%.

Ultra-low resistivity Al + implanted 4H–SiC obtained by microwave annealing and a protective graphite cap

In this work, we have employed a graphite cap for rapid microwave annealing of aluminum implanted 4H–SiC, in the temperature range of 1750–1900 °C, for 30 s durations. The graphite cap prevailed even for 1900 °C/30 s microwave annealing yielding a low surface roughness of 2.4 nm. Rutherford backscattering-channeling spectra indicated that 1900 °C microwave annealing is much more effective than 1800 °C/5 min conventional furnace annealing in not only alleviating the implantation-induced lattice damage but also in removing some of the defects introduced during growth of the 4H–SiC epi-layer used for the Al + implantation. Van der Pauw–Hall measurements indicated an extremely low sheet resistance of 2.8 kΩ/□ for the 1900 °C/30 s annealing, which is about 5 times smaller than the sheet resistance measured on the 1800 °C/5 min conventional furnace annealed material.

Hyperfine interaction studies in diamond

Some of the physical and chemical properties of diamond make it an ideal material for optoelectronic devices capable of operating over a wide frequency bandwidth, with high thermal throughput, and at high operational temperatures. This has stimulated considerable research in using ion implantation methods to incorporate suitable dopant ions in the diamond lattice. Several hyperfine interaction methods have been applied to study the nature of the implantation sites of the different ions in diamond and the annealing of implantation-induced lattice damage. Recent investigations using 19F-time differential perturbed angular distributions (TDPADs), 12B β-NMR, 111In- and 181Hf-perturbed angular correlations (PACs), and Mössbauer studies using 57Co source, recoil-implanted 57Fe * and ion-implanted 57Mn *, are reviewed and their main results are presented.

Raman Scattering Characterization of Implanted ZnO

ABSTRACTIn this work we investigate the lattice damage induced in ZnO implanted with potential group V acceptors by means of Raman scattering. ZnO samples were implanted with N and P to high doses and Raman spectra were obtained prior and after rapid thermal annealing (RTA). Characteristic disorder-activated modes are observed in the spectra that can be used to assess the degree of lattice damage. ZnO samples were also implanted with native Zn+ and O+ ions under similar conditions to study specific effects of implantation with N+ and P+. As revealed by the intensity of disorder-activated bands, the implantation induced lattice damage is considerably higher for Zn+ than for the lighter O+ ion. In samples implanted with N+ additional Raman peaks emerge that are not observed either in the samples implanted with the native Zn+ and O+ ions or in the samples implanted with P+, thus pointing to a local vibrational mode of N or a N complex as the origin of these modes. Disorder-activated features are fully removed by RTA, indicating a high degree of lattice recovery by RTA even for the heavily damaged ZnO samples implanted with Zn+.

Role of boron for defect evolution in hydrogen-implanted silicon

The mechanism underlying the exfoliation phenomenon in B+H coimplanted Si is presented. Compared with only H implantation, H-implanted Si samples that received a B preimplant were observed to have a decrease in implantation-induced lattice damage, in spite of enhanced blistering behavior, which was more pronounced for nonactivated B. Infrared spectroscopy showed that the concentration of Si–H multivacancy defects was also decreased in the B+H coimplanted Si relative to H-only-implanted Si. These decreases in the damage and H-defect density suggest that the lower damage in the B+H coimplanted Si results from a reduction in H-trap density, which in turn enhances H diffusion and the kinetics of blistering. This reduction in lattice damage and H–Si-defect complexes is attributed to the formation of a kinetically active B–Si interstitial complex that is prevalent in nonactivated B-implanted Si.

Raman scattering and photoluminescence studies on O+ implanted silicon

The effects of 125 keV oxygen ion implantation with fluences from 10 14 to 10 16 ions/cm 2 on (1 0 0) cut crystalline silicon (c-Si) have been investigated by Raman scattering and photoluminescence techniques. A systematic decrease in the area and frequency of longitudinal optical (LO) phonon Raman mode and increase in its full-width at half-maximum (FWHM) have been observed with increase of fluence. The temperature at the incident laser spot on the implanted Si increases with fluence. The behavior of peak position and FWHM is due to implantation-induced lattice damage. The decrease in area of the mode is due to the decrease in the volume fraction of c-Si in the implanted layer. The disappearance of the Raman LO mode of c-Si and the appearance of the Raman mode for the amorphous Si (a-Si) have been observed for 10 16 O + /cm 2 fluence, suggesting the amorphization of the implanted layer. The increase in the temperature is due to the poor thermal conductivity of a-Si and increased photon absorption due to implantation induced lattice disorder. Photoluminescence (PL) in the range of 1.8–2.52 eV shows a peak at 2.35 eV with 0.4 eV FWHM for all fluences. Its area increases with fluence and saturates. These results are due to a-Si nanozones created by the O + impact and coalesce of such nanozones at high fluences. The average size of the a-Si nanozone estimated from PL peak position (2.05 nm) and that from the critical fluence for amorphization (1.9 nm) match very well.

Effect of N + ion implantation on n-GaN

We analysed the effect of 70 keV nitrogen ion implantation in n-GaN to 10 14–10 16 cm −2 dose by optical absorption, Raman spectroscopy and photoluminescence. Optical absorption spectra of unimplanted samples gave a band gap of 3.4 eV. On implantation with N +, the optical absorption was noticeable at energy below the band gap, also presumably, arising out of defects and disorder produced by ion implantation. E 2 (high) and A 1 (LO) Raman modes of GaN layer have been observed and analysed. The behavior of Raman shift and FWHM of GaN modes with N + dose are explained on the basis of implantation-induced lattice damage. The PL spectra of unimplanted samples showed a peak at 3.4 eV corresponding to the band gap of GaN and an emission at 2.3 eV which is normally attributed to N Ga antisite defects. On irradiation with N + ion there was a drastic increase in the intensity of emission at 2.3 eV. This suggests that the defect responsible for the emission of 2.3 eV increases on N + implantation. At higher doses, additional emission bands at 2.2 and 2.45 eV were observed in the PL spectra, which might be due to the defect complexes.

Defect Recovery in AlN and InN after Heavy Ion Implantation

The annealing of implantation induced lattice damage in AlN and InN was studied by means of the perturbed angular correlation (PAC) technique using the PAC probes 181Hf(181Ta) and 111In(111Cd). In AlN substantial fractions of the probe atoms occupied substitutional, undisturbed lattice sites after annealing. A detailed investigation of the changes observed during an isochronous annealing programme indicates differences in the recovery process. After In implantation AlN shows considerable annealing of lattice damage already at unexpectedly low temperatures below 600 °C. For Hf implantation AlN experiences a “reverse annealing” effect. For the measurements in InN the PAC results show evidence of In clusters, which are easily formed during the growth of InN or InGaN.

Raman scattering studies on B + implanted Cd 0.96Zn 0.04Te thin films

Cd 0.96Zn 0.04Te thin films were prepared by vacuum evaporation onto glass substrates kept at room temperature. X-ray diffraction (XRD) studies revealed that the as-deposited films have zinc blende structure with preferential (1 1 1) orientation. Raman peak of the as-deposited film appeared between 139.88 and 163.40 cm −1 for the transverse optic and the longitudinal optic phonons, respectively. These films were implanted with 100 keV boron ions to various doses from 10 12 to 10 14 ions/cm 2. The XRD patterns of the irradiated films exhibited a decrease in peak intensity and increase in the FWHM of the (1 1 1) peak. The Raman peak position did not change appreciably whereas the FWHM increases with the ion dose and the results are attributed to the effect of implantation-induced lattice damage.

Raman investigations on nitrogen ion implantation effects on semi-insulating InP

Raman scattering measurements on liquid-encapsulated Czochralski-grown Fe-doped semi-insulating InP(1 0 0) single crystal substrates have been carried out before and after 120 keV N + implantation for various doses from 10 13 to 10 15 cm −2 and also after post-implantation rapid thermal annealing of these samples. It is observed that LO phonon mode frequency decreases and full width at half maximum (FWHM) increases with fluence due to implantation-induced lattice damage. Forbidden Raman TO mode in (1 0 0) cut InP is observed at the doses of 5×10 13 and 5×10 14 cm −2. This might have appeared due to the polycrystalline and/or misoriented regions created during implantation. TO mode is not observed for high doses in as-implanted samples due to excessive lattice damage induced by the implantation. On rapid thermal annealing at 573 K for 30 s, the implanted samples show a partial recovery of LO phonon mode frequency and FWHM due to partial annealing of the damage. On partial annealing of the implantation-induced defects, TO mode FWHM decreases and area under the peak increases for all the doses from 10 13 to 10 15 cm −2.