Search

Purpose This paper aims to systematically demonstrate a methodology to determine the relative and absolute encapsulation efficiencies (αRe and αAb) for thermally- and chemically-robust inorganic pigments, typically like ZrSiO4-based pigments, thereby enhancing their coloring performance. Design/methodology/approach The authors designed a route, surplus alkali-decomposition and subsequently strong-acid dissolution (SAD2) to completely decompose three classic zircon pigments (Pr–ZrSiO4, Fe2O3@ZrSiO4 and CdS@ZrSiO4) into clear solutions and preferably used inductively coupled plasma-optical emission spectrometry (ICP-OES) to determine the concentrations of host elements and chromophores, thereby deriving the numeric data and interrelation of αRe and αAb. Findings Zircon pigments can be thoroughly decomposed into some dissoluble zirconate–silicate resultants by SAD2 at a ratio of the fluxing agent to pigment over 6. ICP-OES is proved more suitable than some other quantification techniques in deriving the compositional concentrations, thereby the values of αRe and αAb, and their transformation coefficient KRA, which maintains stably within 0.8–0.9 in Fe2O3@ZrSiO4 and CdS@ZrSiO4 and is slightly reduced to 0.67–0.85 in Pr–ZrSiO4. Practical implications The SAD2 method and encapsulation efficiencies are well applicable for both zircon pigments and the other pigmental or non-pigmental inhomogeneous systems in characterizing their accurate composition. Originality/value The authors herein first proposed strict definitions for the relative and absolute encapsulation efficiencies for inorganic pigments, developed a relatively stringent methodology to determine their accurate values and interrelation.

Room temperature electroluminescence in the eye safe region of the spectrum over the range 1.7–2.1 μm is demonstrated from a thulium doped silicon diode. The same room temperature photoluminescence can be attained on a silicon-on-insulator substrate. The emission lines are from the first excited to ground state of the Tm3+ ion, 3F4→3H6. A detailed study has been made to establish the optimum implant and processing conditions for efficient room temperature luminescence. The importance of the correct placement of the thulium ions with respect to the depletion region edge and dislocation loops formed upon boron implantation has been established. Tm3+ has been demonstrated to lase in other systems and is the basis of widely applied, commercial, optically pumped 2 μm lasers. The demonstration of electroluminescence in silicon and luminescence on an SOI platform are necessary prerequisites for the potential development of Tm injection lasers and optical amplifiers.

Erbium implanted silicon as a quantum technology platform has both telecommunications and integrated circuit processing compatibility. In Si implanted with Er to a concentration of 3x10^17 cm^3 and O to a concentration of 10^20 cm^3, the electron spin coherence time, T2, and the spin-lattice relaxation time, T1, were measured to be 7.5 ls and ~1 ms, respectively, at 5 K. The spin echo decay profile displayed strong modulation, which was consistent with the super-hyperfine interaction between Er3{\th} and a spin bath of 29Si nuclei. The calculated spectral diffusion time was similar to the measured T2, which indicated that T2 was limited by spectral diffusion due to T1-induced flips of neighboring Er3{\th} spins. The origin of the echo is an Er center surrounded by six O atoms with monoclinic C1h site symmetry., Comment: arXiv admin note: substantial text overlap with arXiv:2006.00225

Erbium-implanted silicon is promising for both photonic and quantum-technology platforms, since it possesses both telecommunications and integrated-circuit processing compatibility. However, several different \ud Er\ud centers are generated during the implantation and annealing process, the presence of which could hinder the development of these applications. When \ud Si\ud is coimplanted with \ud 10\ud 17\ud cm\ud −\ud 3\ud \ud Er\ud and \ud 10\ud 20\ud cm\ud −\ud 3\ud \ud O\ud ions, and the appropriate annealing process is used, one of these centers, which is present at higher \ud Er\ud concentrations, can be eliminated. Characterization of samples with \ud Er\ud concentrations of

The interest in the G-centre is driven by reports that it can lase in silicon. To further this, the transfer of this technology from bulk silicon to a silicon-on-insulator (SOI) platform is an essential requirement to progress to lasing and optical amplification on silicon. We report on the efficient generation of the lasing G-centre in SOI substrates by proton irradiation of carbon ion implants. Following carbon implantation samples were annealed and then proton irradiated to form the G-centre and characterized by photoluminescence measurements. The temperature dependence of the emission and the behaviour of the G-centre with post proton annealing were investigated and results are compared with identical implants in control samples of bulk silicon. Overall, we find that the optically active G-centre can be up to 300% brighter and has better survivability over a wider process window in SOI than in bulk silicon.

This study reports the effect of an increasing ion dose on both the electrical activation yield and the characteristic properties of implanted bismuth donors in silicon. A strong dependence of implant fluence is observed on both the yield of bismuth donors and the measured impurity diffusion. This is such that higher ion concentrations result in both a decrease in activation and an enhancement in donor migration through interactions with mobile silicon lattice vacancies and interstitials. Furthermore, the effect of implant fluence on the properties of the Si:Bi donor bound exciton, D0X, is also explored using photoluminescence (PL) measurements. In the highest density sample, centers corresponding to the PL of bismuth D0Xs within both the high density region and the lower concentration diffused tail of the implanted donor profile are identifiable.

Silicon underpins microelectronics but lacks the photonic capability needed for next-generation systems and currently relies on a highly undesirable hybridization of separate discrete devices using direct band gap semiconductors. Rare-earth (RE) implantation is a promising approach to bestow photonic capability to silicon but is limited to internal RE transition wavelengths. Reported here is the fi rst observation of direct optical transitions from the silicon band edge to internal f -levels of implanted REs (Ce, Eu, and Yb); this overturns previously held assumptions about the alignment of RE levels to the silicon band gap. The photoluminescence lines are massively redshifted to several technologically useful wavelengths and modeling of their splitting indicates that they must originate from the REs. Eu-implanted silicon devices display a greatly enhanced electroluminescence effi ciency of 8%. Also observed is the fi rst crystal fi eld splitting in Ce luminescence. Mid-IR silicon photodetectors with specifi c detectivities comparable to existing state-of-theart mid-IR detectors are demonstrated.

The effects of helium ion irradiation on immiscible AlN/TiN multilayered system were studied. The structure consisted of 30 alternate AlN (similar to 8 nm) and TiN (similar to 9.3 nm) layers of a total thickness around 260 nm, deposited on (100) Si substrates by reactive sputtering. The system was then implanted with 30 keV He+ to very high irradiation doses, 1-4 x 10(17) ions/cm(2). Evaluated projected ion range was 153.1 +/- 45.4 nm and maximum displacements per atom for the applied doses from 6 to 24. It was found that the multilayers remained well separated and stable after irradiation to 1 x 10(17) ions/cm(2), which introduces up to 10 at.% of He within the structure. The main effects were agglomeration of He bubbles around the projected ion range, mostly concentrated at the AlN edges of the interfaces, and a slight increase of the mean grain size within the affected zone. Increasing of the ion dose induced further agglomeration of bubbles, splitting of the layers at the interfaces, and final destruction of the structure. The evaluated He content was consistent with the implanted dose up to 2 x 10(17) ions/cm(2). For the highest dose the implanted gas is partially released from the structure. The results can be interesting towards the development of radiation tolerant materials. (C) 2015 Elsevier B.V. All rights reserved. 16th International Conference on Thin Films (ICTF), Oct 13-16, 2014, Dubrovnik, Croatia

We report waveguides in Ni-doped Li2O–Ga2O3–SiO2 (Ni:LGS) glass and glass–ceramic (GC) fabricated with a femtosecond (fs) laser with repetition rate of 1 kHz. When the glass is annealed to form a GC, the waveguides are erased. However, in the GC the waveguides are not erased by annealing. In Ni:LGS GC a 415 nm absorption band was created by fs laser waveguide writing due to the creation of Ni nanoparticles with an estimated diameter of a few nm. Raman and photoluminescence spectra of the bulk and waveguide structures were indistinguishable; however, fluorescence decay profiles indicated more long lifetime components in the waveguide compared to the bulk.

By measuring the centroid of a beam on a detector, one can track the movement of that beam across the detector. By tracking this movement, one can track the object encompassing the detector, for example, a spacecraft. A variety of system-specific performance inhibitors can make this a challenge, requiring a robust calibration method. The goal of this investigation is to model the true beam position of the instrument in terms of the measured beam position. For this, a mathematical model is created that interpolates and corrects the measured beam position using precollected position data—a "calibration model." The real-world scenario for this investigation is the flight-representative model of the fine lateral and longitudinal sensor (FLLS) instrument, built by Neptec Design Group and Neptec UK for the European Space Agency mission PROBA-3. Performance inhibitors for FLLS are cropping of the beam, imperfect optics, and a varying distance the beam has traveled (up to 250 m). Using bivariate spline interpolation for the FLLS calibration model gives the best performance, achieving a measurement accuracy well within the mission requirement of

We report a new approach of generating the dicarbon G-centre on silicon substrates by utilizing technique that is fully compatible with the standard silicon ultra-large-scale integration (ULSI) technology. Silicon wafers were implanted with carbon and irradiated with high energy protons to produce self-interstitials that are crucial in the formation of the G-centre. Prior to that, all the samples were pre-amorphised with germanium. Photoluminescence (PL) measurements at 80 K were carried out to investigate the point defect mediated luminescence of the G-centre with a wavelength of 1280 nm. The results show a prominent, sharp luminescence at the carbon related, G centre in majority of the samples.

The optically active carbon related G-center is attracting great interest because of evidence that it can provide lasing in silicon. Here a technique to form the G-center in silicon is reported. The carbon G-center is generated by implantation of carbon followed by proton irradiation. Photoluminescence measurements confirm the controlled formation of high levels of the G-center that, importantly, completely dominates the emission spectrum. Unlike previous methods of introducing the G-center the current approach significantly is truly fully compatible with standard silicon ULSI (ultralarge scale integration) technology.

The effects of argon ion irradiation on structural changes in Ta/Ti multilayers deposited on Si wafers were investigated. The starting structures consisted of sputter deposited 10 alternate Ta (similar to 23 nm) and Ti (similar to 17 nm) layers of a total thickness similar to 200 nm. They were irradiated at room temperature with 200 key Ar(+), to the fluences from 5 x 10(15) to 2 x 10(16) ions/cm(2). The projected ion range was around mid-depth of the multilayered structure, and maximum displacements per atom similar to 130. It was found that, despite of the relatively heavy ion irradiation, individual nanocrystalline Ta and Ti layers remain unmixed, keeping the same level of interface planarity. The changes observed in the mostly affected region are increase in lateral dimensions of crystal grains in individual layers, and incorporation of bubbles and defects that cause some stretching of the crystal lattice. Absence of interlayer mixing is assigned to Ta-Ti immiscibility (reaction enthalpy Delta H(f) = +2 kJ/mol). It is estimated that up to similar to 5 at.% interface mixing induced directly by collision cascades could be compensated by dynamic demixing due to chemical driving forces in the temperature relaxation regime. The results can be interesting towards developing radiation tolerant materials based on multilayered structures. (C) 2011 Elsevier B.V. All rights reserved.

We review progress in silicon LEDs using dislocation engineering to achieve high temperature operation, a process that is fully CMOS (Complementary Metal Oxide Semiconductor) compatible. We concentrate on devices operating in the near infra-red where high value applications are. The need for silicon emitters, lasers and optical amplifiers is discussed followed by an outline of previous approaches and possible future routes explored. Results on gain in silicon are reported and routes to electrically pumped injection lasers and optical amplifiers considered. Extension of 1.1 and 1.5 μm devices to other wavelengths is discussed

In this paper, we first introduce and discuss the current state-of-the-art in integrated silicon photonic technology. We argue that the only missing link to the incorporation of this technology into mainstream high end silicon chips and systems are the availability of fully integrated silicon light sources and amplifiers. We go onto describe how dislocation engineering can be used to nano-engineer, locally, the strain in optically active silicon devices to enable high operating temperatures. We show how, by combining this approach with the incorporation of rare earths, that have optical levels in the near infra-red below the silicon band-gap, a potential route exists to meet these needs. In particular, we show that the use of erbium, together with dislocation engineering, could provide useful optical emission and gain at the important 1.5 μm wavelength that dominates optical data transfer.

Photoluminescence in the 1.2–1.35 μm range has been observed in silicon substrates incorporating thulium in the trivalent Tm 3+ state and co-doped with boron. The results showed eight sharp lines at 1211.5, 1231.0, 1250.8, 1269.3, 1283.8, 1290.6, 1311.3 and 1326.0 nm, corresponding to known internal Tm 3+ transitions in the manifold from the 3 H 5 to the 3 H 6 ground states. The luminescence was strongly dependent on the sample fabrication processes. In this paper we will discuss the influence of Tm implantation parameters and post-implant annealing conditions on the photoluminescence response of silicon doped with Tm 3+ .

This study reports on high energy bismuth ion implantation into silicon with a particular emphasis on the effect that annealing conditions have on the observed hyperfine structure of the Si:Bi donor state. A suppression of donor bound exciton, D0X, photoluminescence is observed in implanted samples which have been annealed at 700°C relating to the presence of a dense layer of lattice defects that is formed during the implantation process. Hall measurments at 10K show that this implant damage manifests itself at low temperatures as an abundance of p‐type charge carriers, the density of which is observed to have a strong dependence on annealing temperature. Using resonant D0X photoconductivity, we are able to identify the presence of a hyperfine structure in samples annealed at a minimum temperature of 800°C; however, higher temperatures are required to eliminate effects of implantation strain.

A metal–oxide–silicon (MOS) tunneling light-emitting diode is fabricated with ion-beam-synthesized β-FeSi2 precipitates embedded in the active region. Fe ions were implanted into p−-100 silicon substrate at cryogenic temperature (∼−120 °C), followed by rapid thermal oxidation (RTO). Under constant voltage biased in accumulation and at temperatures down to 80 K, electroluminescence (EL) with wavelength peaking at ∼1.5 μm is observed at a current density of about 2.0 A/cm2. Light output increases linearly with current density. Temperature dependence of the EL shows that the luminescence is due to interband recombination in the crystalline precipitates. The strain in these isolated precipitates may contribute to the luminescence properties of β-FeSi2 in silicon.

We have studied the influence of the ion species, ion energy, fluence, irradiation temperature and post-implantation annealing on the formation of shallow dislocation loops in silicon, for fabrication of silicon light emitting diodes. The substrates used were (100) Si, implanted with 20-80 keV boron at room temperature and 75-175 keV silicon at 100 and 200 degrees C. The implanted fluences were from 5 x 10(14) to 1 x 10(15) ions/cm(2). After irradiation the samples were processed for 15 s to 20 min at 950 degrees C by rapid thermal annealing. Structural analysis of the samples was done by transmission electron microscopy and Rutherford backscattering spectrometry. In all irradiations the silicon substrates were not amorphized, and that resulted in the formation of extrinsic perfect and faulted dislocation loops with Burgers vectors a/2 LT 110 GT and a/3 LT 111 GT , respectively, sitting in {111} habit planes. It was demonstrated that by varying the ion implantation parameters and post-irradiation annealing, it is possible to form various shapes, concentration and distribution of dislocation loops in silicon. (C) 2008 Elsevier B.V. All rights reserved. 9th European Conference on Accelerators in Applied Research and Technology, Sep 03-07, 2007, Florence, Italy

We report on the super enhancement of the 1.54 μm Er emission in erbium doped silicon-on-insulator when codoped with oxygen at a ratio of 1:1. This is attributed to a more favourable crystal field splitting in the substitutional tetrahedral site favoured for the singly coordinated case. The results on these carefully matched implant profiles show that optical response is highly determined by the amount and ratio of erbium and oxygen present in the sample and ratios of O:Er greater than unity are severely detrimental to the Er emission. The most efficient luminescence is forty times higher than in silicon-on-insulator implanted with Er only. This super enhancement now offers a realistic route not only for optical communication applications but also for the implementation of silicon photonic integrated circuits for sensing, biomedical instrumentation and quantum communication.

Silicon-based, light emitting diodes (LEDs) and light emitting structures without electrical contacts have been integrated on silicon-on-insulator (SOI) wafers. The room temperature characterization of these samples using electro- and photo-luminescence is described. All samples emit at 1150 nm near the band-edge of Si, and samples that receive Er implantation emit additionally at a band centered at 1550 nm. Photoluminescence from the SOI wafers shows a strong influence from the optical cavity created by the Si/SiO2 structure. This effect is corrected using a classical plane-wave model. The importance of this procedure is highlighted for the rigorous interpretation of the luminescent spectrum from any SOI system. The external quantum efficiency of the LEDs is measured to be 8.7 ? 10?6. The potential impact on this efficiency resulting from the structure of diodes fabricated on SOI rather than bulk silicon is discussed.

Thin layers of nanocrystalline FeSi 2 embedded in Si structures have been formed by Fe implantation using a metal vapor vacuum arc (MEVVA) ion source under various implantation and thermal annealing conditions. The microstructures were studied in details and correlated with the photoluminescence (PL) properties. It is found that higher lattice coherence between the FeSi 2 nanocrystals and the Si matrix is associated with better light emission efficiency. Multiple-cycle implantation schemes were introduced and it is shown that with appropriate process design the dose quenching effect can be suppressed to achieve light emission enhancement in higher dose samples. De-convolution of the PL spectra into two or three peaks was performed and their temperature and excitation power dependence were analyzed. The analysis results indicate that the 1.55-μm emission really originated from FeSi 2 and that the emission peaks are likely donor- or accepted-level-related. MOS structures with the incorporation of implanted nanocrystalline FeSi 2 were fabricated. Electroluminescence (EL) spectra from these devices showed two peak features of which one peak corresponds to FeSi 2 emission and the other corresponds to enhanced Si band-edge emission. Clear room-temperature EL signals from these device structures were observed. A model is proposed to qualitatively understand the temperature dependence of the EL spectra.

FeSi2 precipitates with various structural properties embedded within silicon matrix were formed by iron ion implantation using a metal vapor vacuum arc ion source followed by thermal annealing at various conditions. The microstructure and phase properties of the implanted samples were studied by transmission electron microscopy. The orientation relationships and thus the interfacial coherence between the FeSi2 precipitates and the Si matrix were observed to change with the annealing conditions. A good correlation is identified in-between the structural properties and the photoluminescence properties of these samples.

PACS 61.72.Tt, 62.50.+p, 78.55.Ap, 85.60.Bt, 85.60.Jb We report the influence of excitation wavelength and pressure effects on the photoluminescence (PL) of silicon light-emitting diode material fabricated by boron ion implantation. The PL spectra show an anomalous increase in total intensity as temperature elevates, and this luminescence is found to be strongest with decreasing laser penetration depth away from the sample surface. The PL peak position shifts towards lower energy at a rate of -14 meV/GPa with increasing pressure. This rate agrees with earlier optical measurements on the band-edge absorption of silicon, confirming that this luminescence is closely related to phonon-assisted indirect band gap transitions.

The dislocation engineered approach makes use of the controlled introduction of dislocation loops into silicon substrates by conventional ion implantation and thermal processing. The dislocation loops introduce a local strain field, which modifies the band structure and provides spatial confinement of the charge carriers, thus allowing strong intrinsic silicon band-edge luminescence to be observed at room temperature. Efficient silicon-based dislocation engineered light emitting diodes were fabricated under different process conditions to study the influence of the dislocation loops formation on the luminescence properties. Electroluminescence and transmission electron microscopy techniques were used to characterise the devices and the results showed that (i) the size and density of the loops vary with boron implant energy and post-implant anneal conditions and (ii) the luminescence response from such devices can be directly related to the size and density of the dislocation loops.

This article presents a study of the possibilities of optimising the electroluminescence (EL) efficiency of dislocation-engineered silicon light-emitting diodes (DELEDs). The diodes were produced by implantation of boron in n-type (100)Si wafers, at a constant ion energy and fluence, of 30 keV and 1×1015 ions/cm2, respectively. The density and the areal coverage by dislocation loops were varied by applying different annealing times in a rapid thermal processing, from 30 s to 60 min. It is shown that the EL efficiency is directly correlated to the number and areal coverage by the loops. The highest population of loops, ∼5×109 /cm2, and an areal coverage of around 50% were achieved for 1–5 min annealing. This loop distribution results in optimal DELEDs, having the highest EL response and the largest increase of EL intensity with operating temperature (80–300 K). The results of this work confirm a previously introduced model of charge-carrier spatial confinement by a local stress induced by the edge of the dislocation loops, preventing carrier diffusion to non-radiative recombination centres and enhancing radiative transitions at the silicon band edge.

In this paper, a general overview of the technologies surrounding light emission in silicon-based systems is presented with an indication as to the applications for which they may be used. Special attention is given to the use of dislocation engineering, where, through the use of additional dopants, not only can 1150-nm band edge emission be achieved but tuning of the wavelength to accommodate telecommunications applications is also possible. Details of the impact of implantation energy and dose are demonstrated together with post implant anneal studies to optimise the process for light generation. Finally, dislocation engineering is applied to silicon on insulator (SOI), the most common optical platform.

Nanometer-sized β-FeSi 2 precipitates are formed in Si by ion beam synthesis (IBS). A systematic study is carried out to investigate the correlation among the implantation parameters, the microstructure, and the luminescence properties. On the one hand, we found additional orientation relationships (ORs) appear between the β-FeSi 2 and the Si with improved lattice coherence between the two, when the ion implantation energy is increased. On the other hand, the degree of preferential orientation deteriorates and leads to poor lattice coherence between the particles and Si matrix when the iron ion is overdosed. These microstructure changes lead to different luminescence properties (intensity, peak position and shape) of the β-FeSi 2 particles accordingly.

Silicon MOS structures with FeSi 2 precipitates embedded in the MOS active region have been fabricated and the electroluminescence (EL) properties from these FeSi 2 –Si MOS structures were measured as a function of temperature from 80 K to 300 K. Clear EL signals were observed even at room temperature for samples prepared at appropriate processing conditions. The EL spectra consist of two peaks, one attributed to FeSi 2 and the other attributed to Si band edge emission. While the intensity of the FeSi 2 peak showed the usual thermal quenching behavior, the Si band edge emission showed the opposite trend with its intensity increased with increasing temperature. Details of the line shapes and their temperature dependence are analyzed and discussed.

We give a brief overview of the development and recent progress of a new technology, silicon dislocation-engineered light-emitting diodes (LEDs). The dislocation-engineering method enables the development of light emitters in conventional silicon technology. Key and probably unique to this approach is its genuine and total compatibility with the standard ultra-large-scale integration (ULSI) process used to produce complex computer chips.

In this paper, experimental results of a study on iron disilicide light-emitting diodes will be presented. A comparison will be made between the luminescence characteristics of standard iron disilicide diodes and diodes that have been augmented by the use of dislocation engineering, using dislocation loops, to provide spatial localisation of the injected carriers. The improvements observed will be discussed and the results kinetically modelled using a rate equation approach.

Iron implantation into Si using a metal vapor vacuum arc ion source has been carried out either at a low temperature (LT) of about −100 °C or at an elevated temperature of about 380 °C, to synthesize nanometer scale β-FeSi 2 precipitates in Si. The samples were characterized using transmission electron microscopy (TEM) and photoluminescence (PL). The TEM results showed that while there were plenty of dislocation loops in the high temperature implanted sample, no dislocation loop was observed in the LT implanted sample. From the differences in the PL spectra, in conjunction with the TEM results, the origins of the PL peaks in different samples could be distinguished and identified to be from β-FeSi 2 precipitates or from crystal defects in the samples.

Room temperature β-FeSi2 light emitting diodes have been fabricated by conventional ULSI processes using a recently developed dislocation engineering approach. The devices were fabricated by iron implantation into pre-grown abrupt silicon p–n junctions followed by low energy boron implantation to form the dislocation loops. Room temperature emission at ∼1.6 μm was obtained from most of the dislocation engineered devices, in contrast to standard ion beam synthesised β-FeSi2 diodes, where no electroluminescence was observed.

In this paper we investigate the formation of b-FeSi2 (from co-deposited layers of Fe and Si produced by ion beam assisted deposition) under a number of annealing regimes (annealing temperatures between 100 and 900 C and times up to 18 h) by optical characterisation of the band edge parameters. The results have indicated that both annealing temperatures and times have a strong effect on the number of defects underneath the fundamental edge of absorption. The measurement temperature dependency of the band gap is also found to be dependent on the annealing conditions. 2002 Published by Elsevier Science B.V.

The existence of amorphous semiconducting FeSi2, having a direct band gap of 0.88 eV. is demonstrated. It was synthesized by ion beam mixing of 50 nm Fe on Si(1 0 0) with 120 keV Ar-8 ions, at 300 degreesC. Rapid diffusion of Si to the surface is assigned to be the dominating process that results in the formation of amorphous FeSi2 phase, Other Synthesis techniques should be possible for fabrication of this material. and it Could be applied in large area electronics, (C) 2002 Published by Elsevier Science B.V. 7th European Conference on Accelerators in Applied Research and Technology, Aug 21-24, 2001, Univ Surrey, Guildford, England

The photoreflectance spectra of ion beam synthesized β-FeSi2 reveals a direct gap at 0.815 eV and are shown to agree with the band gap value obtained by photoluminescence once the adjustments for the temperature difference and trap related recombination effects are made. This provides very convincing evidence for intrinsic light emission from ion beam synthesized β-FeSi2. Furthermore, we propose a simple model that helps to clarify the variety of inconsistent results obtained by optical absorption measurements. When the results of photoluminescence and photoreflectance are inserted into this model, we obtain good agreement with our measured optical absorption results.

Carrier-type reversal to enable the formation of semiconductor p-n junctions is a prerequisite\ud for many electronic applications. Chalcogenide glasses are p-type semiconductors and their\ud applications have been limited by the extraordinary difficulty in obtaining n-type conductivity.\ud The ability to form chalcogenide glass p-n junctions could improve the performance of\ud phase-change memory and thermoelectric devices and allow the direct electronic control of\ud nonlinear optical devices. Previously, carrier-type reversal has been restricted to the GeCh\ud (Ch¼S, Se, Te) family of glasses, with very high Bi or Pb ‘doping’ concentrations (B5–11\ud at.%), incorporated during high-temperature glass melting. Here we report the first n-type\ud doping of chalcogenide glasses by ion implantation of Bi into GeTe and GaLaSO amorphous\ud films, demonstrating rectification and photocurrent in a Bi-implanted GaLaSO device.\ud The electrical doping effect of Bi is observed at a 100 times lower concentration than for Bi\ud melt-doped GeCh glasses.

The impact of Bi implantation on the conductivity and the thermopower of GeTe, Ge-Sb-Te, and Ga- La-S films is investigated. The enhanced conductivity appears to be notably sensitive to a dose of an implant. Incorporation of Bi in amorphous chalcogenide films at doses up to 1x1015 cm-2 is seen not to change the majority carrier type and activation energy for the conduction process. Higher implantation doses may reverse the majority carrier type in the studied films. Electron conductivity was observed in GeTe films implanted with Bi at a dose of 2x1016 cm-2. These studies indicate that native coordination defects present in amorphous chalcogenide semiconductors can be deactivated by means of ion implantation. A substantial density of implantation-induced traps in the studied films and their interfaces with silicon is inferred from analysis of the space-charge limited current and capacitance-voltage characteristics taken on Au/amorphous chalcogenide/Si structures., Comment: arXiv admin note: substantial text overlap with arXiv:1410.5677

We report amorphous GaLaSO-based resistive switching devices, with and without Pb-implantation before deposition of an Al active electrode, which switch due to deposition and dissolution of Al metal filaments. The devices set at 2–3 and 3–4 V with resistance ratios of 6 × 104 and 3 × 109 for the unimplanted and Pb-implanted devices, respectively. The devices reset under positive Al electrode bias, and Al diffused 40 nm further into GaLaSO in the unimplanted device. We attribute the positive reset and higher set bias, compared to devices using Ag or Cu active electrodes, to the greater propensity of Al to oxidise.

Doping of amorphous chalcogenide films of rather dissimilar bonding type and resistivity, namely, Ga-La-S, GeTe, and Ge-Sb-Te by means of ion implantation of bismuth is considered. To characterize defects induced by ion-beam implantation space-charge-limited conduction and capacitance-voltage characteristics of amorphous chalcogenide/silicon heterojunctions are investigated. It is shown that ion implantation introduces substantial defect densities in the films and their interfaces with silicon. This comes along with a gradual decrease in the resistivity and the thermopower coefficient. It is shown that conductivity in GeTe and Ge-Sb-Te films is consistent with two-type carrier conduction model. It is anticipated that ion implantation renders electrons to become less localized than holes leading to electron conductivity in certain cases as, for example, in GeTe. The modification of electronic properties which stems from the ion-solid interaction processes results in the modification of the composition of the films as identified by elemental analyses with the help of Rutherford Backscattering Spectrometry. At the same time, much higher interface trap densities are observed in the implanted chalcogenide/silicon interfaces. In terms of interface trap built-up, ion implantation influences Ge-Sb-Te and Ga-La-S interfaces with silicon distinctly different. Much higher density of acceptor-like interface trap is observed in Ga-La-S/Si interfaces suggesting the ion-beam induced interface traps are not solely due to silicon dangling bond defect.

The thermodynamic properties and phase diagrams of the Ru–Si and Os–Si systems are assessed. The calculated enthalpies of fusion and entropies of fusion of ruthenium and osmium silicides are compared with the reported values of different transition metal silicides. Both the thermodynamic properties and the phase diagrams of Ru–Si and Os–Si systems are in good agreement with the available experimental data.

This paper presents a study of the synthesis of β-FeSi2 layers by irradiation of Fe/Si bilayers with Fe+ ions and a consequent thermal processing, and the analysis of their properties. Characterization of samples included RBS, XRD, cross-section HRTEM, and photo-absorption measurements. It was found that homogenous, highly ordered 275 nm β-FeSi2 layers can be grown by implantation of 90 nm Fe on Si, with 200 keV Fe+ ions at 500°C, followed by 3.5 h annealing at 870°C.

β-FeSi2/Si light emitting devices (LEDs) have been attracting great interest since the first successful demonstration of an ion beam synthesised (IBS) device operating at a wavelength of 1.5 μm . We report here on a study of the electrical, electronic and optical properties of devices produced by Fe implantation into epitaxial silicon layers. The devices have been characterised by current–voltage (I–V), capacitance–voltage (C–V), deep level transient spectroscopy (DLTS) and electroluminescence (EL) measurements. DLTS showed the presence of a majority carrier trapping centre, with an activation energy of 200±25 meV. Room temperature EL was observed from β-FeSi2/Si LEDs. Preliminary analysis of the EL results suggests its quench ratio depends on device structure; the quenching is thought to be related to surface recombination.

A systematic study of excitation of the 4 f –4 f luminescence of Er 3+ ions near 1.5 μm in SiO 2 layers codoped with Yb and containing Si-nanocrystals (nc-Si) is presented. Layers of SiO 2 were implanted with Er + and Yb + ions at the energies of 800 and 830 keV, respectively, at a wide range of doses (0.5–4.0×10 15 cm −2 ). Photoluminescence (PL) and PL excitation spectroscopy were applied to study excitation of Er 3+ ions. The Yb 3+ ions were found to play a key role in sensitizing the PL of Er 3+ for pump wavelengths ∼500 nm and 1μm. Models of sensitization processes involving energy transfer from Yb-centers are discussed. Silicon nanocrystals were produced by high dose Si implantation into SiO 2 (excess Si contents ∼7%) followed by annealing at 1100°C. An evidence is presented that transfer of energy from nc-Si is not the dominant mechanisms of excitation of Er 3+ ions. Defect mediated mechanisms seem to be more efficient. It is also found that excess Si in SiO 2 prevents clustering of rare earth atoms.

Proton irradiation at an energy of 1 MeV has been used to create an approximately even distribution of simple point defects in both Cz and FZ, n-type silicon to a depth of greater than 10 μ m. The implanted dose ranged from 1×1011 to 1×10 16 cm −2 . The vacancy component of the defect concentration has been quantitatively measured using positron annihilation and deep level transient spectroscopy. Through careful experimental design it has been possible to meaningfully compare the concentrations independently determined using the two approaches. Good agreement is found between the two techniques for the FZ material adding credence to the methods through which defect concentrations are obtained from the primary data. Somewhat less reasonable agreement is found for the Cz material for which one possible explanation is offered.

The Raman spectra of ion beam synthesized (IBS) β-FeSi2 are investigated and evidence for the presence of a net tensile stress is presented. Possible origins of the observed stress are suggested and a simple model is proposed in order to calculate a value of the observed stress. A correlation between the tensile stress, the nature of the band gap, and the resulting light emitting properties of IBS β-FeSi2 is suggested.

A p-type device grade silicon wafer was implanted by 1 MeV Ru+ ions to a dose of 5.67 × 1016 cm−2. The microstructures of the as-implanted and annealed samples were studied mainly by analytical transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results showed that the implantation resulted in a well-defined surface layer of about 910 nm in thickness. The layer was composed of ultra-fine Ru2Si3 crystallites in an amorphous matrix. After annealing, the inner part of the layer recovered completely to single crystal Si with nano-scaled Ru2Si3 embedded in it. A ∼660 nm thick polycrystalline region consisting of Si and Ru2Si3 grains was formed at the surface.