Concurrent Sputtering Research Articles

Self-organized vertically aligned single-crystal silicon nanostructures with controlled shape and aspect ratio by reactive plasma etching

The formation of vertically aligned single-crystalline silicon nanostructures via “self-organized” maskless etching in Ar+H2 plasmas is studied. The shape and aspect ratio can be effectively controlled by the reactive plasma composition. In the optimum parameter space, single-crystalline pyramid-like nanostructures are produced; otherwise, nanocones and nanodots are formed. This generic nanostructure formation approach does not involve any external material deposition. It is based on a concurrent sputtering, etching, hydrogen termination, and atom/radical redeposition and can be applied to other nanomaterials.

Effect of ion-irradiation induced defects on the nanocluster Si∕Er3+ coupling in Er-doped silicon-rich silicon oxide

The effect of ion-irradiation induced defects on the nanocluster Si∕Er3+ coupling in Er-doped silicon-rich silicon oxide (SRSO) thin film is investigated. Er-doped SRSO, which consists of silicon nanoclusters (nc-Si) in a SiO2 matrix, was fabricated using electron-cyclotron resonance plasma enhanced chemical vapor deposition using SiH4 and O2 with concurrent sputtering of Er followed by a high temperature annealing. Defects were introduced into the film via irradiation with 3MeV Si ions and subsequently removed by high temperature annealings. The authors find that ion irradiation reduces Er3+ luminescence from SRSO films, even when the excitation cross section and luminescence efficiency of Er3+ ions are completely restored. On the other hand, ion irradiation increases the intrinsic nc-Si luminescence and has little effect on the Er3+ luminescence from a similarly prepared, Er-doped SiO2 film, indicating that the presence of irradiation induced defects in the initial amorphous film can reduce the number of Er3+ ions available for nc-Si mediated luminescence by as much as a factor of 3.

Time dependent preferential sputtering in the HfO 2 layer on Si(100)

The time dependent preferential sputtering in the HfO 2 layer on Si(100) has been investigated in-situ with X-ray photoelectron spectroscopy during Ar ion sputtering. Hf4f, O1s, and Si2p spectra show that three bonding environments (Hf 0+ from the Hf metal, Hf 2+ from HfO, and Hf 4+ from HfO 2) co-exist inside the HfO 2 layer during sputtering. The Hf 4+ doublet decreases with sputtering time in an exponential-like function. Both Hf 0+ and Hf 2+ doublets increase with sputtering time in opposite ways. Two concurrent sputtering mechanisms characterizing the formation of HfO and Hf due to preferential sputtering of oxygen within the HfO 2 layer can well explain the detailed bond breaking and re-formation process. The Hf metal is the final product and the HfO is an intermediate product during sputtering under vacuum. The HfO cannot be removed and acts as a residual component in the HfO 2 layer.

Interfacial characteristic of graded hydroxyapatite and titanium thin film by magnetron sputtering

Graded film of calcium phosphate and titanium (Ti) was prepared on Ti-6Al-4V alloy by radio-frequency magnetron sputtering. Concurrent sputtering of HA and Ti for four times, The area proportions of HA to Ti in the targets are 20%, 50%, 90% and 100% respectively, contributes a gradual distribution of Ca, P, O and Ti across the interface of film and alloy substrate. The graded HA/Ti film is formed by annealing for 1 h at 600 °C water vapour flow. The tensile adhesion strength of graded sputtered and annealed HA/Ti film is approximately 35 Mpa, which is an obvious advantage compared with monolithic HA film. The results obtained from the nanoindentation test show that Young's modulus and microhardness of graded HA/Ti film are also graded distribution and strain reversion was much better than that in the monolithic HA film.

Excitation mechanism of visible, Tb3+ photoluminescence from Tb-doped silicon oxynitride

The excitation mechanism of visible luminescence from Tb3+-doped silicon oxynitride is investigated. Tb-doped silicon oxynitride films were deposited by inductive-coupled plasma-enhanced chemical vapor deposition of SiH4, O2, and N2 with concurrent sputtering of Tb. Luminescences from both the host matrix and the Tb3+ intra-4f transition are observed, but no correlation is found between them as the composition and the annealing conditions were varied. Photoluminescence excitation spectroscopy shows a strong increase in the Tb3+ luminescence intensity as the pump energy is increased above 3.5eV while the host matrix luminescence decreases. Taken together, the results that there is little energy transfer between band-tail states of silicon oxynitride and Tb3+, and that efficient excitation of Tb3+ by carriers requires excitation of carriers into the extended states of oxynitride.

Nd3+ photoluminescence and its implication on the excitation mechanisms of Nd3+ in Nd doped hydrogenated amorphous silicon alloyed with carbon

Nd3+ photoluminescence from Nd doped, hydrogenated amorphous silicon alloyed with carbon (a-Si:H:C) is investigated. Nd-doped, a-Si:H:C films were deposited using electron cyclotron resonance plasma enhanced chemical vapor deposition of SiH4 and CH4 with concurrent sputtering of Nd. Clear Nd3+ luminescence peaks can be observed when excited with 488nm light, indicating that Nd3+ ions in a-Si:H:C are excited via carriers generated in the a-Si:H:C. The energetics of Nd-doped a-Si:H:C rule out defect-related Auger excitation via mid-gap states. Based on the temperature and pump power dependence of Nd3+ and intrinsic a-Si:H:C photoluminescence intensities, we identify excitation via Nd-related defects with a strong coupling to Nd3+ as a possible excitation mechanism for Nd in a-Si:H:C.

Controlling Er–Tm interaction in Er and Tm codoped silicon-rich silicon oxide using nanometer-scale spatial separation for efficient, broadband infrared luminescence

The effect of nanometer-scale spatial separation between Er3+ and Tm3+ ions in Er and Tm codoped silicon-rich silicon oxide (SRSO) films is investigated. Er and Tm codoped SRSO films, which consist of nanocluster Si(nc-Si) embedded inside SiO2 matrix, were fabricated with electron cyclotron resonance-plasma enhanced chemical vapor deposition of SiH4 and O2 with concurrent sputtering of Er and Tm metal targets. Spatial separation between Er3+ and Tm3+ ions was achieved by depositing alternating layers of Er- and Tm-doped layers of varying thickness while keeping the total film thickness the same. The films display broadband infrared photoluminescence (PL) from 1.5 to 2.0μm under a single source excitation due to simultaneous excitation of Er3+ and Tm3+ ions by nc-Si. Increasing the layer thickness from 0 to 72nm increases the Er3+ PL intensity nearly 50-fold while the Tm3+ PL intensity is unaffected. The data are well-explained by a model assuming a dipole–dipole interaction between excited Er3+ and Tm3+ ions, and suggest that by nanoscale engineering, efficient, ultrabroadband infrared luminescence can be obtained in an optically homogeneous material using a single light source.

Enhancement of Er3+ Luminescence from Er-doped Hydrogenated Amorphous Silicon by Carbon Co-doping

The effect of C co-doping on the Er3+ luminescence properties of Er-doped hydrogenated amorphous Si (a-Si:H) is investigated. Er-doped a-Si:H thin films co-doped with C were deposited using electron–cyclotron resonance plasma enhanced chemical vapor deposition of SiH4 and CH4 with concurrent sputtering of Er. We find that C co-doping greatly increases the room temperature 1.54 µm Er3+ photoluminescence (PL) intensity, with the maximum enhancement by a factor of 4 being obtained at a C concentration of ∼15 at.%. Part of the reason for such enhancement is the suppression of the temperature quenching of the Er3+ PL intensity and liftime, which we attribute to the increased optical bandgap of a-Si:H due to C co-doping. However, unlike other co-dopants such as O that also can enhance the Er3+ PL, C co-doping does not degrade the a-Si:H film quality, demonstrating its suitability for developing Si-based optoelectronic devices.

De-excitation mechanisms of Er 3+ in Er-doped hydrogenated amorphous silicon prepared by electron cyclotron resonance plasma enhanced chemical vapor deposition

The de-excitation mechanisms of Er 3+ in Er-doped hydrogenated amorphous silicon prepared by electron cyclotron resonance plasma enhanced chemical vapor deposition of SiH 4 and concurrent sputtering of Er is investigated. As the temperature is raised from 25 to 288 K, the Er 3+ luminescence intensity decreases by a factor of 3 as does its decay time, indicating that activation of non-radiative decay paths for excited Er 3+ ions dominates the thermal quenching of Er 3+ luminescence. Based on the analysis of the temperature dependence of the Er 3+ luminescence decay time, we identify interaction with the defect state near the midgap as the possible back-transfer channel.

Structure, bonding state and in-vitro study of Ca–P–Ti film deposited on Ti6Al4V by RF magnetron sputtering

Experimental investigation of functionally graded calcium phosphate-based bio-active films on Ti–6Al–4V orthopaedic alloy prepared in an RF magnetron sputtering plasma reactor is reported. The technique involves concurrent sputtering of Hydroxyapatite (HA) and Ti targets, which results in remarkably enhanced adhesion of the film to the substrate and stability of the interface. The films have been characterized using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The XPS data show that the films are composed of O, Ca, P and Ti, and reveal the formation of OP groups and hybridization of O–Ca–P. The XRD pattern shows that the Ca–P thin films are of crystalline calcium oxide phosphate (4CaO·P 2O 5) with preferred orientation varying with processing parameters. High-resolution optical emission spectra show that the emission of CaO is dominant. The CaO, PO and CaPO species are strongly influenced by deposition conditions. The introduction of Ti element during deposition provides a stable interface between bio-inert substrates Ti–6Al–4V and bioactive HA coating. In-vitro cell culturing tests suggest excellent biocompatibility of the Ca–P–Ti films.

RF magnetron sputtering deposition of bioactive Ca-P-based coatings on Ti-6Al-4V alloy

RF magnetron concurrent sputtering of hydroxyapatite and Ti forming functionally graded calcium phosphate-based composite bioactive films on Ti-6Al-4V orthopedic alloy is reported. Calcium oxide phosphate (4CaO/spl middot/P/sub 2/O/sub 5/) is the main crystalline phase. In vitro cell culturing tests suggest outstanding biocompatibility of the Ca-P-Ti films. Images of the plasma-enhanced sputtering processes and cell culturing are presented and discussed.

Stoichiometry, crystallinity, and nano-scale surface morphology of the graded calcium phosphate-based bio-ceramic interlayer on Ti-Al-V

ABSTRACTA plasma-assisted concurrent Rf sputtering technique for fabrication of biocompatible, functionally graded CaP-based interlayer on Ti-6Al-4V orthopedic alloy is reported. Each layer in the coating is designed to meet a specific functionality. The adherent to the metal layer features elevated content of Ti and supports excellent ceramic-metal interfacial stability. The middle layer features nanocrystalline structure and mimics natural bone apatites. The technique allows one to reproduce Ca/P ratios intrinsic to major natural calcium phosphates. Surface morphology of the outer, a few to few tens of nanometers thick, layer, has been tailored to fit the requirements for the bio-molecule/protein attachment factors. Various material and surface characterization techniques confirm that the optimal surface morphology of the outer layer is achieved for the process conditions yielding nanocrystalline structure of the middle layer. Preliminary cell culturing tests confirm the link between the tailored nano-scale surface morphology, parameters of the middle nanostructured layer, and overall biocompatibility of the coating.

Stoichiometry, crystallinity, and nano-scale surface morphology of the graded calcium phosphate-based bio-ceramic interlayer on Ti-Al-V

ABSTRACTA plasma-assisted concurrent Rf sputtering technique for fabrication of biocompatible, functionally graded CaP-based interlayer on Ti-6Al-4V orthopedic alloy is reported. Each layer in the coating is designed to meet a specific functionality. The adherent to the metal layer features elevated content of Ti and supports excellent ceramic-metal interfacial stability. The middle layer features nanocrystalline structure and mimics natural bone apatites. The technique allows one to reproduce Ca/P ratios intrinsic to major natural calcium phosphates. Surface morphology of the outer, a few to few tens of nanometers thick, layer, has been tailored to fit the requirements for the bio-molecule/protein attachment factors. Various material and surface characterization techniques confirm that the optimal surface morphology of the outer layer is achieved for the process conditions yielding nanocrystalline structure of the middle layer. Preliminary cell culturing tests confirm the link between the tailored nano-scale surface morphology, parameters of the middle nanostructured layer, and overall biocompatibility of the coating.

Optical gain at 1.54 μm in erbium-doped silicon nanocluster sensitized waveguide

Optical gain at 1.54 μm in erbium-doped silicon-rich silicon oxide (SRSO) is demonstrated. Er-doped SRSO thin film was fabricated by electron-cyclotron resonance enhanced chemical vapor deposition of silicon suboxide with concurrent sputtering of erbium followed by a 5 min anneal at 1000 °C. Ridge-type single mode waveguides were fabricated by wet chemical etching. Optical gain of 4 dB/cm of an externally coupled signal at 1.54 μm is observed when the Er is excited via carriers generated in the Si nanoclusters by the 477 nm line of an Ar laser incident on the top of the waveguide at a pump power of 1.5 W cm−2.

Deposition and 1.54 μm Er3+ luminescent properties of erbium-doped hydrogenated amorphous silicon thin films by electron cyclotron resonance plasma enhanced chemical vapor deposition of SiH4 with concurrent sputtering of erbium

Erbium-doped hydrogenated amorphous silicon (a-Si:H) thin films were deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition of SiH4 with concurrent sputtering of erbium. The oxygen and carbon contamination levels in all films were 1×1019 and 3×1019 cm−3, respectively, and the erbium concentrations could be controlled from 0.13 to 1.1 at. % by adjusting the erbium bias voltage. The half width Γ/2 of the Raman transverse-optic peak of the deposited films ranged from 32±1 to 36±1 cm−1, increasing with the increasing Er concentration. Strong 1.54 μm Er3+ luminescence with little temperature quenching was observed from all samples. The most intense Er3+ luminescence was observed from the as-deposited film with a deposition temperature of 380 °C and an erbium concentration of 0.13 at. %, showing that using the present method, erbium-doped a-Si:H films with good erbium optical activity and low structural disorder can be deposited directly while avoiding excessive contamination.

Waveguiding and 1.54 μm Er3+ Photoluminescence Properties of Erbium Doped Silicon Rich Silicon Oxide

AbstractThe waveguiding and 1.54 μm Er3+ photoluminescent properties of Er doped silicon-rich silicon oxide (SRSO) are investigated. Erbium-doped SRSO films, which consist of nanocrystalline Si clusters embedded inside Si0 2 matrix, were deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition of SiH4 and O2 with concurrent sputtering of erbium. The excess Si content of the SRSO films ranged from 0 to 10 at. %, and Er content ranged from 0.01 to 0.3 at. %. After deposition, films were rapid thermal annealed at temperatures between 750 and 1150°C for durations ranging from 2 to 20 min. to precipitate silicon nanoclusters. All films show strong room temperature 1.54 μm Er3+ photoluminescence. The luminescence lifetimes that can be > 6 msec. The refractive indices of the SRSO films range from 1.48 to 2.47, increasing with increasing excess Si content. Thus, waveguides can be formed easily by depositing erbium doped SRSO films on 1 μm thick SiO2 films. Furthermore, carrier-induced de-excitation mechanisms of excited erbium atoms in SRSO are nearly completely suppressed in such SRSO films, indicating that population inversion of Er3+ ions by carrier-mediated excitation is possible.

Composition dependence of room temperature 1.54 μm Er3+ luminescence from erbium-doped silicon:oxygen thin films deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition

The composition dependence of room temperature 1.54 μm Er3+ photoluminescence of erbium-doped silicon:oxygen thin films produced by electron cyclotron resonance plasma enhanced chemical vapor deposition of SiH4 and O2 with concurrent sputtering of erbium is investigated. The Si:O ratio was varied from 3:1 to 1:2 and the annealing temperature was varied from 500 to 900 °C. The most intense Er3+ luminescence is observed from the sample with a Si:O ratio of 1:1.2 after a 900 °C anneal and the formation of silicon nanoclusters embedded in the SiO2 matrix. The high active erbium fraction, efficient excitation via carriers, and high luminescence efficiency due to the high quality SiO2 matrix are identified as key factors in producing the intense Er3+ luminescence.

Composition dependence of room temperature 1.54μm Er3+ luminescence from erbium doped silicon:oxygen thin films deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition

AbstractThe composition dependence of room temperature 1.54 μ Er3+ photoluminescence of erbium doped silicon:oxygen thin films deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition of SiH4 and O2 with concurrent sputtering of erbium is investigated. The Si:O ratio was varied from 3:1 to 1:2 and the annealing temperature was varied from 500 to 900 °C. The most intense Er3+ luminescence is observed from the sample with Si:O ratio of 1:1.2 after 900 °C anneal and formation of silicon nanoclusters embedded in SiO2 matrix. High active erbium fraction, efficient excitation via carriers, and high luminescence efficiency due to high quality SiO2 matrix are identified as key factors in producing the intense Er3+ luminescence.

Residue formation on Si surfaces in a CHF3 discharge environment

Ion beam simulation techniques are used to study fluorocarbon residue formation and substrate composition and structure modifications of silicon by CHF3 plasma environment. Fluorocarbon residues are shown to grow by direct ion incorporation or ion activated growth processes in ion beams over the energy range 50–1000 eV. At ion energy >150 eV concurrent sputtering of the overlayer film results in a steady state film thickness of ∼30 Å, relatively independent of ion energy. Films are fluorine deficient, with C/F ratio of 1–3 depending on ion energy, dose, and film thickness. Energetic ion (300 eV) penetration of the film results in continuous Si etching and substantial substrate modification. For 560 eV ion energy an ion-mixed interfacial layer of approximately 25 Å thickness is produced which contains substantial O, C, and F. A deeper (>150 Å) damaged layer is observed due to H+ implantation. Removal of overlayer films and interfacial layers by standard cleaning procedures is addressed.

High dose ion implantation in yttria-stabilized zirconia

Abstract High dose 56Fe implantations (15–110 keV) in oxygen ion conducting solid solutions of 0.86 Zr02-0.14 YO1.5 [ZY14] are used to introduce electronic conductivity. The Fe distribution in the target as a function of the various implantation parameters (dose, acceleration voltage) has been studied. Different profile shapes can be obtained. A combination of a high surface concentration and a rather flat profile in a surface layer is possible. Strong deviations from the normally expected Gaussian distribution are found after high dose implantation due to sputtering effects. However, if the sputter yield is experimentally determined, good prediction of the implanted dopant distribution is still possible. The peak concentration of high dose distributions is situated at or close to the surface. This surface peak concentration is obtained at a steady-state situation of concurrent sputtering and implantation of Fe. A maximum surface concentration with respect to Zr(Fe/Zr = 1.0) is achieved with the highest implantation energy used (110 keV) because the sputter yield is relatively low as compared with lower energies. After prolonged heat treatment in air (800°C, 24–60 hours) of the samples implanted with a high dose Fe, Fe203-rich surface layers are formed. Rutherford Backscattering Spectrometry (RBS) is used for the profile analyses in combination with Auger Electron Spectroscopy (AES).