Single Energy Implantation Research Articles

Optical planar waveguides in photo-thermal-refractive glasses fabricated by single- or double-energy carbon ion implantation

Ion implantation has demonstrated to be an efficient and reliable technique for the fabrication of optical waveguides in a diversity of transparent materials. Photo-thermal-refractive glass (PTR) is considered to be durable and stable holographic recording medium. Optical planar waveguide structures in the PTR glasses were formed, for the first time to our knowledge, by the C3+-ion implantation with single-energy (6.0 MeV) and double-energy (5.5+6.0 MeV), respectively. The process of the carbon ion implantation was simulated by the stopping and range of ions in matter code. The morphologies of the waveguides were recorded by a microscope operating in transmission mode. The guided beam distributions of the waveguides were measured by the end-face coupling technique. Comparing with the single-energy implantation, the double-energy implantation improves the light confinement for the dark-mode spectrum. The guiding properties suggest that the carbon-implanted PTR glass waveguides have potential for the manufacture of photonic devices.

Electron microscopy profiling of ion implantation damage in diamond: Dependence on fluence and annealing

The doping of diamond by ion implantation has been feasible for 25years, but with the proviso that low dose implants can be annealed whereas high dose implants “graphitize”. An understanding of the types of defects, and their depth profiles, produced during the doping/implantation of diamond remains essential for the optimization of high-temperature, high-power electronic applications. This study focuses on investigating the nature of the radiation damage produced during the implantation of carbon ions into synthetic type Ib and natural diamonds using a spread of 4 energies, corresponding to typical doping energies, according to the CIRA (Cold-Implantation-Rapid-Annealing) routine, as well as a single energy implantation at room temperature. Both conventional and high resolution cross-sectional electron microscopies were achieved and used to analyze the implanted diamonds in conjunction with electron energy loss spectroscopy (EELS) and selected area diffraction (SAD). The cross sections were obtained using two different preparation methods.For low fluence implantations, using the CIRA routine, it is confirmed that the damaged diamond regains its crystallinity after annealing at 1600K. However, above the amorphization threshold fluence, followed by rapid annealing at 1600K, the whole implanted layer consisted of primarily amorphous carbon. High resolution TEM shows that the implanted layer consists of nano-regions with bent (002) graphitic planes and regions of amorphous carbon. The interface between the implanted layer and the diamond substrate near end of range shows diamond nanocrystallites, interspersed between regions of amorphous carbon and with bent (002) graphitic planes. There is no evidence for epitaxial regrowth. For high dose single energy ion implantation at room temperature, the unannealed layer shows a high degree of disorder at the maximum ion range, with some alignment of basal planes related to graphitic carbon, but with some of the diamond structure still partially intact. The implanted range included a diamond layer above the damaged region. This diamond layer showed no evidence of amorphous carbon.

Leaky mode suppression in planar optical waveguides written in Er:TeO2–WO3 glass and CaF2 crystal via double energy implantation with MeV N+ ions

Ion implantation proved to be an universal technique for producing waveguides in most optical materials. Tellurite glasses are good hosts of rare-earth elements for the development of fibre and integrated optical amplifiers and lasers covering all the main telecommunication bands. Er3+-doped tellurite glasses are good candidates for the fabrication of broadband amplifiers in wavelength division multiplexing around 1.55μm, as they exhibit large stimulated cross sections and broad emission bandwidth. Calcium fluoride is an excellent optical material, due to its perfect optical characteristics from UV wavelengths up to near IR. It has become a promising laser host material (doped with rare earth elements). Ion implantation was also applied to optical waveguide fabrication in CaF2 and other halide crystals. In the present work first single-energy implantations at 3.5MeV at various fluences were applied. Waveguide operation up to 1.5μm was observed in Er:Te glass, and up to 980nm in CaF2. Then double-energy implantations at a fixed upper energy of 3.5MeV and lower energies between 2.5 and 3.2MeV were performed to suppress leaky modes by increasing barrier width.

Single- and double energy N+ ion irradiated planar optical waveguides in Er: Tungsten–tellurite oxide glass and sillenite type Bismuth Germanate crystals working up to telecommunications wavelengths

Ion implantation proved to be a universal technique for producing waveguides in most optical materials. Tellurite glasses are good hosts of rare-earth elements for the development of fibre and integrated optical amplifiers and lasers covering all the main telecommunication bands. Er3+-doped tellurite glasses are good candidates for the fabrication of broadband amplifiers in wavelength division multiplexing around 1.55μm, as they exhibit large stimulated cross sections and broad emission bandwidth. Fabrication of channel waveguides in such a material via N+ ion implantation was reported recently. Sillenite type Bismuth Germanate (BGO) crystals are good nonlinear optical materials. Parameters of waveguide fabrication in both materials via implantation of MeV-energy N+ ions were optimized. First single-energy implantations at 3.5MeV at various fluences were applied. Waveguide operation up to 1.5μm was observed in both materials. Then double-energy implantations at a fixed upper energy of 3.5MeV and lower energies between 2.5 and 3.1MeV were performed to suppress leaky modes by increasing barrier width. Improvement of waveguide characteristics was found by m-line spectroscopy and spectroscopic ellipsometry.

Vacancy-type defects created by single-shot and chain ion implantation of silicon

Vacancy-type defects created by single-energy implantation of Czochralski-grown single-crystal silicon by 4 MeV silicon ions at doses of 1012 and 1013 cm−2 have been compared with those created by an energy chain of implants of 0.4, 0.9, 1.5, 2.2 and 4 MeV ions, each at one-fifth of the single-energy dose. Measurements were taken for as-implanted samples and after annealing to temperatures up to 600 °C. In contrast to the expectation that a more uniform depth distribution of interstitials and vacancies would lead to a more efficient recombination and consequently fewer surviving vacancies, vacancy-related damage survived in the chain-implanted samples to higher temperatures, before almost complete annealing at 600 °C. It is therefore concluded that it is the absolute initial monovacancy concentration, rather than any initial separation of vacancy- and interstitial-rich regions, that determines the probability of survival as divacancies, and that there exists a threshold divacancy concentration of 1–2 × 1018 cm−3 for clustering at 400–500 °C.

Differential Hall effect profiling of ultrashallow junctions in Sb implanted silicon

A differential Hall effect technique has been developed to obtain doping profiles at a depth resolution down to 2nm with junction depths of about 20nm. We have determined the electrical characteristics of 5×1014Sb+cm−2 implanted in (100) silicon at an energy of 5keV. A comparison was made between carrier concentration profiles and secondary ion mass spectroscopy measurements of the atomic profiles as a function of annealing temperature. We have profiled single energy implants of antimony and also double implants; the latter enables complete profiles to be measured down to the background level of about 1018cm−3.

Investigation of optical waveguide formed in Er:Yb:phosphate glass by MeV He+ implantation

Planar waveguide was fabricated in Er:Yb:phosphate glass by a single energy implantation of 2.5 MeV He+ at a dose of 1.6 × 1016 ions/cm2. The waveguide was characterized by prism coupling method, and the refractive index profile was reconstructed using the inverse Wentzel-Kramers-Brillouin method. The photoluminescence was also measured. The energy loss was simulated, and the results were compared and discussed with respect to the refractive index profile in the waveguide.

Analysis of optical waveguide formed in x-cut Yb:GdCOB crystal by He + implantation

The planar optical waveguide was fabricated in x-cut Yb:GdCOB crystal by a single energy implantation of 2.5 MeV He + at a dose of 1.6×10 16 ions/cm 2. The guided modes were characterized by m-line spectra with prism coupler. The refractive index profile in the crystal waveguide was reconstructed on the basis of parameterized index profile method. The energy loss was simulated by the TRIM (transport of ions in matter) code, and the results were investigated in comparison with the refractive index profile in the waveguide.

Mode gaps in the refractive index properties of low-dose ion-implanted LiNbO3 waveguides

Data are presented for the refractive index profiles for low-dose He+ ion-implanted LiNbO3 waveguides. In the nuclear stopping region, the extraordinary index is increased for low ion doses, by contrast with index reduction normally associated with ion-implanted waveguiding structures. The index increase was confirmed by fabricating a buried waveguide for the extraordinary index by use of multi-energy implants. For single-energy implants, data are shown which map the extraordinary index at the surface together with that in the nuclear collision zone, as a function of angle relative to the z axis of light propagation in surface waveguides for X and Y cut LiNbO3. These indices cross over near 45°, which results in a mode gap for which waveguide modes are not supported. A mechanism for this behavior is discussed based on defect-induced lattice relaxation. The phenomenon of a controlled mode gap may have applicability for optoelectronic and nonlinear materials and devices.

Characterization of 3C-SiC doped by nitrogen implantation

Doping by ion implantation, in addition to the introduction of dopants during material growth, is the only method available to obtain the required electronic activation in SiC and is also capable of providing area selective doping. Results presented here were obtained from implantations of nitrogen in the energy range from 50 to 180 keV. Implantations were performed as single energy implants in order to allow a comparison of the implanted profiles with theory. Theoretical profiles are calculated by Monte Carlo simulation using the TRIM code. Profiles from the simulation and secondary ion mass spectroscopy measurements were fitted using Pearson distributions. From this procedure the parameters projected range, straggle, kurtosis and skewness were extracted. The projected ranges obtained vary almost linearly with implantation energy from 83 nm (50 keV) to 261 nm (180 keV). The activation of the implanted impurities was measured by the Hall method. The influence of different implantation parameters on activation is discussed.

Doping of 3C-SiC by implantation of nitrogen at high temperatures

Doping profiles and electrical properties are investigated on SiC samples doped with single energy implants from nitrogen. The profiles are analyzed using Pearson distributions for different implantation energies and temperatures. Implantations are performed for temperatures up to 1200°C. Diffusion during high temperature implantation is investigated and the diffusion coefficients measured range from 1.09 × 10−15 to 1.53 × 10−14cm2/s depending on temperature. The activation energy for implantation enhanced diffusion is estimated to be 0.91 eV. A comparison is made with diffusion during annealing. The activated dopants from high temperature implantation are investigated by the Hall probe method, showing that activation and mobility increase with temperature.

Analysis of refractive index profile in KTiOPO 4 waveguide formed by 3.0 MeV He + implantation

The optical waveguide formation in X-cut KTiOPO 4 was achieved by single energy implantation of 3.0 MeV He + to a total dose of 2.0×10 16ions/cm 2 at liquid nitrogen temperature. The modes were examined by the prism (LiTaO 3) coupling method. The analysis of the refractive index profile in the KTiOPO 4(100) waveguide was performed based on parametrized index profile reconstruction (PIPR). We have used the TRIM (the transport of ions in matter) code to simulate the energy loss distribution. The result shows that the nuclear collision mostly influences the refractive index profile, but the peak position of the refractive index profile is shallower than that of the nuclear energy loss distribution.

Formation and characterization of Si/SiO2 multilayer structures by oxygen ion implantation into silicon

Buried double oxide structures in Si have been produced by the sequential high- and low-energy implantation of oxygen ions at 2 MeV and 90 keV, respectively. Each implantation step was followed by a high-temperature anneal at 1300 °C for 6 h. Fourier transform infrared reflection spectroscopy has been used in order to characterize the as-implanted and annealed samples. Rutherford backscattering spectroscopy/channeling analysis was also carried out for selected samples. The morphology of the two buried layers is the same as for the single energy implants. No interaction or transport of oxygen between the two layers is observed. The in-between buried Si layer as well as the Si overlayer are of high crystal quality and could be potentially used as waveguiding layers, in a Si-based optical waveguiding structure.

PN junction formation in 6HSiC by acceptor implantation into n-type substrate

A1 and B implantations were performed into n-type 6H-bulk SiC and epitaxial layers at both room temperature and 850°C. Annealings were performed in the temperature range of 1100–1650°C in a SiC crucible. For single-energy implants, the implant gettered to the 0.7 R p location for annealing temperatures ≥1400°C. For the 850°C implanted samples the RBS yield in the annealed material is comparable to the yield in the as-grown material, indicating a good lattice recovery. A maximum activation of 18% for Al-implanted samples was observed. PN junction diodes were made using Al-implanted material.

Amorphization of silicon by high dose germanium ion implantation with no external cooling mechanism

Si(100) wafers were implanted by using three different methods: single-energy Ge + ion implantation, double-energy Ge + and Ge 2+ ion implantation, and double-energy Si + and Ge + ion implantation. The single-energy implantations were performed at energies from 50 to 180 keV, over the range of 8.38 × 10 15 to 5.80 × 10 16 ions/cm 2. By keeping the ion beam power density below 0.09 W/cm 2, full surface amorphization could be achieved in the single-energy Ge + implanted samples. Also beam heating was suppressed during implantation, although the implanter had no external cooling. In addition, a two-step single-energy implant technique using sequentially high and low power densities was further developed in order to reduce implantation times. In order to locate the amorphous/crystalline (a/c) interfaces far away from the concentration peak positions of the implanted Ge + ions, the double-energy Ge + and Ge 2+, and Si + and Ge + implantations were carried out. Three Ge + implanted wafers were either pre-implanted with 180 keV Si + ions, or post-implanted with 360 keV Ge 2+ ions, respectively, in order to locate deeper a/c interfaces. Channelling effect measurements indicate that the double-energy Ge + and Ge 2+ implantation is a preferable technique for wilfully tailoring the amorphous depth and the Ge peak position.

Fabrication of planar optical waveguides in LiB/sub 3/O/sub 5/ by 2 MeV He/sup +/ ion implantation

The fabrication of planar optical waveguides in LiB/sub 3/O/sub 5/ is discussed. Using 2-MeV /sup 4/He/sup +/ implantation with a dose of 1.5*10/sup 16/ ions/cm/sup 2/ at 300 K, the refractive indexes of a 0.2- mu m-thick layer 5.1 mu m below the crystal surface are reduced to form optical barrier guides. For this ion dose the maximum change from the bulk values of refractive index at a wavelength of 0.488 mu m are 1.5%, 5.25%, and 4% for n/sub x/, n/sub y/, and n/sub z/, respectively. The refractive indexes of the guiding region change by less than 0.02% from the bulk values. The dose dependence of the optical barrier height has been measured. A threshold ion dose of about 0.75*10/sup 16/ ions/cm/sup 2/ is required to form a refractive index barrier and ion doses higher than about 2.5*10/sup 16/ ions/cm/sup 2/. saturate the refractive index decrease. Waveguide propagation losses for annealed single energy implants of dose 1.5*10/sup 16/ ions/cm/sup 2/ are dominated by tunneling and are estimated to be approximately 8.9 dB/cm for the z-cut waveguides used. Multiple energy implants broaden the optical barrier, and losses of <4 dB/cm have been observed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Low-loss optical channel waveguides in KNbO3 by multiple energy ion implantation

Permanent optical channel waveguides in single crystals of KNbO3 are formed with low-dose MeV He ion irradiation. A single energy implantation forms a confinement barrier at the projected range of the ions whereas multiple energy implantations combined with a positive shielding mask form the side walls. Guiding modes are produced and propagation losses as low as 1.0 dB/cm are measured without the need for any annealing. The irradiation induced refractive index changes that define the boundaries of the waveguiding channels are made visible with cross-polarized light microscopy.

Electrochemical study of multiple-energy nitrogen-ion-implanted aluminium alloys

Nitrogen-implanted aluminium is reported to show a better pitting corrosion resistance. However, the corrosion behaviour depends on the number of nitrogen atoms available on the surface and the thickness of the implanted layer. In single-energy implantations the number of nitrogen atoms available on the surface is less than that in the bulk because of the Gaussian nature of the depth profile obtained. To overcome this difficulty, we decided to obtain a thick implanted layer and a flat depth profile by using multiple-energy implantations. Aluminium specimens were implanted with N + ions in energy steps of 80, 35 and 15 keV to a total dose of 4.6×10 17 N + cm −2 to obtain a layer of implanted surface 2000 Å thick. The implanted specimens were tested for corrosion resistance in Na 2SO 4 solutions at different pH values ranging from acidic to basic conditions. Cathodic and anodic polarization curves, corrosion potential and polarization resistance vs. time plots were obtained for implanted and unimplanted specimens. The samples were also characterized by scanning electron microscopy and Auger electron spectroscopy before and after the corrosion test. The electrochemical behaviour of the implanted samples appears quite different with respect to the unimplanted ones and the corrosion resistance improves in the acidic environment.

Electrical Properties of n- and p-type In0.53Ga0.47As Layers Formed by Ion Implantation and Rapid Thermal(Flash)Anneal

ABSTRACTRapid thermal annealing (4−7s) of 28Si and 9Be implants in VPE-grown In0.53Ga0.47As has produced n- and p-type active layers with controlled doping levels between 1017 and 3×1018 cm−3. The multiple-implant schedules were based on Rp and ΔR data derived from SIMS measurements on single-energy implants. The activated n- and p-type layers have a good surface morphology and 300 K mobilities of 3000–7000 and 100–200 cm2 /V−s, respectively. Data on implant schedules, electrical characteristics, carrier concentration profiles, and Rp /ΔRp information are presented.

Annealing Characteristics of Be Ion Implanted GaAs

350 keV Be ion implantation into semi-insulating GaAs was accomplished at R.T. for doses ranging from 1×1013 to 1×1016 cm-2. To characterize the produced damage, defect conductivity profiling and electron diffraction were carried out for samples annealed below 450°C. Implanted layers were found to be extremely less damaged, even at high doses. To determine the optimum conditions for low resistive p-type layer formation, isochronal annealing characteristics were studied above 700°C. Mobility obtained was equivalent to bulk mobility. At higher doses, annealing, which caused a decrease in activity in GaAs. As a result, low resistive p-type layers were found to be reproducibly formed by relatively low temperature annealing (∼700°C) for high dose implanted samples, giving the lowest sheet resistance of 14 Ω/□ by single energy implantation.