Implantation Temperature Research Articles

Temperature dependence of retention of energetic deuterium and carbon simultaneously implanted into tungsten

The simultaneous implantation of 10keV C+ and 3.0keV D2+ into tungsten was carried out at elevated temperatures to establish the retention mechanism of energetic deuterium and carbon. Thermal desorption spectroscopy showed that the deuterium retention obviously decreased as the implantation temperature increased. All the desorption stages disappeared when the implantation was performed at 673K, indicating no deuterium trapping as C–D bonds was processed in this temperature. The results of X-ray photoelectron spectroscopy and glow discharge-optical emission spectroscopy showed that a mixed carbon layer had been formed during the implantation, resulting from the carbon deposition and accumulation near the surface of tungsten during the implantation. The carbon layer would enhance the chemical sputtering with deuterium and reduce the deuterium retention, as the implantation temperature increases. During discussion, a simple retention mechanism has been proposed, which shows the importance of implantation temperature.

Implantation of HA into Superplastic Ti-6Al-4V: Kinetics and Mechanical Behaviors of Implanted Layer

An implanted layer is produced by implantation of hydroxyapatite (HA) into superplastic Ti-6Al-4V. X-ray diffraction (XRD) analysis indicates that the surface of the implanted layer is composed of HA and Ti-6Al-4V, and line-scanning analysis confirms a mutual elemental diffusion of HA and Ti-6Al-4V. According to the scanning electron microscope (SEM) images, by increasing the implantation temperature, the thickness of the implanted layer increases. The bonding strength between implanted layer and titanium substrate is examined by conducting a friction wear test. Higher surface removal of an implanted layer is observed when as-received Ti-6A1-4V was used in the implantation process, which is an indication of higher bonding strength between implanted layer and superplastic Ti-6A1-4V. The effect of implanted layer thickness on the wear resistance is also investigated. The reduction in thickness of the implanted layer is more evident in thicker implanted layers. The results suggest that the adhesion between the implanted layer and titanium substrate is stronger than the cohesion within the implanted layer.

Temperature dependence of the erosion behavior of deuterium beam exposed tungsten-doped carbon films (a-C:W)

Tungsten-doped amorphous carbon films (a-C:W) are used as model system to study the deuterium (D) retention behavior and the erosion behavior of metal containing co-deposited layers. In our recent studies, the implantation temperature was increased towards an ITER relevant range. Pure and 7.5at% tungsten-doped carbon films have been exposed to a deuterium beam of 200eV/D at different implantation temperatures up to 1300K and at a fluence of 1024D/m2. Rutherford backscattering spectrometry with a 1.5MeV +H beam was performed to obtain the total erosion yield. For each implantation condition and for each structure of doped films, the total erosion yield is reduced significant, compared to pure films. The temperature dependence of the total erosion yield is less pronounced for doped films.

The Phenomenology of Ion Implantation-Induced Blistering and Thin-Layer Splitting in Compound Semiconductors

Hydrogen and/or helium implantation-induced surface blistering and layer splitting in compound semiconductors such as InP, GaAs, GaN, AlN, and ZnO are discussed. The blistering phenomenon depends on many parameters such as the semiconductor material, ion fluence, ion energy, and implantation temperature. The optimum values of these parameters for compound semiconductors are presented. The blistering and splitting processes in silicon have been studied in detail, motivated by the fabrication of the widely used silicon-on-insulator wafers. Hence, a comparison of the blistering process in Si and compound semiconductors is also presented. This comparative study is technologically relevant since ion implantation-induced layer splitting combined with direct wafer bonding in principle allows the transfer of any type of semiconductor layer onto any foreign substrate of choice—the technique is known as the ion-cut or Smart-Cut™ method. For the aforementioned compound semiconductors, investigations regarding layer transfer using the ion-cut method are still in their infancy. We report feasibility studies of layer transfer by the ion-cut method for some of the most important and widely used compound semiconductors. The importance of characteristic values for successful wafer bonding such as wafer bow and surface flatness as well as roughness are discussed, and difficulties in achieving some of these values are pointed out.

Enhanced retained dose uniformity in NiTi spinal correction rod treated by three-dimensional mesh-assisted nitrogen plasma immersion ion implantation

Owing to the nonconformal plasma sheath in plasma immersion ion implantation of a rod sample, the retained dose can vary significantly. The authors propose to improve the implant uniformity by introducing a metal mesh. The depth profiles obtained with and without the mesh are compared and the implantation temperature at various locations is evaluated indirectly by differential scanning calorimeter. Our results reveal that by using the metal mesh, the retained dose uniformity along the length is greatly improved and the effects of the implantation temperature on the localized mechanical properties of the implanted NiTi shape memory alloy rod are nearly negligible.

Effects of Implantation Temperature on Sheet and Contact Resistance of Heavily Al Implanted 4H-SiC

Effects of implantation temperature on electrical properties of heavily-Al-doped 4H-SiC layer formed with Al implantation have been investigated. To form the p++ 4H-SiC with the original 4H-stacking structure, the implantation temperature above 175 °C is needed. A decrease in the implantation temperature below 250 °C leads to an increase in the NA-ND. It is suggested that an increase in the density of vacancies with a decrease in the implantation temperature promotes the Al substitution to lattice sites during activation annealing. The lower-temperature implantation also causes a decrease in activation energy for the p-type electrical conduction and a decrease in p-type ohmic contact resistivity. We presume that the increase in the Al acceptors at low-implantation temperatures gives expansion of the impurity bands and formation of valence band tail-states, causing the decrease in the impurity binding energy. The properties obtained with the lower-temperature implantation are desirable for practical applications especially at low temperatures.

Enhancement of Defect Production Rates in n-Type Silicon by Hydrogen Implantation Near 270 K

Defect production behavior in hydrogen-implanted n-type silicon has been studied by varying the implantation temperature from 88 K to 303 K. Deep-level transient spectroscopy has been used to reveal electron trap spectra for Schottky diodes fabricated at room temperature after implantation. Metastable defects are observed in addition to vacancy- and hydrogen-related defects. It is found that the production rates of these defects are greatly enhanced by hydrogen implantation near 270 K. It is suggested that hydrogen plays an important role in enhancement of defect production rates, since such defect production behavior is not observed in He-implanted samples.

Embedment of HA into Superplastic Ti-6Al-4V: Effects of Implantation Temperature

In this research, we present a method for the embedment of hydroxyapatite (HA) into superplastic Ti6Al4V where the elements of HA and Ti6Al4V diffuse into each other to form a high quality implanted layer. The implantation process into superplastic titanium alloy was divided to two steps; first, the superplastic forming of Ti6Al4V was carried out using high-temperature compression test machine. In the second step, HA was embedded into superplastic Ti6Al4V by using a special designed clamp with an initial compressive load at high temperatures. The EDX and Line Scanning analyses indicate that the resulted film is composed of elements of HA and titanium alloy and due to the diffusion of HA and Ti6Al4V elements into each other, a good embedment is achieved. The elemental diffusion of HA and Ti6Al4V increases by increasing the temperature of the implantation process therefore the thickness of the implanted layer and the hardness of the embedded surface increase with the temperature.

Ion-beam synthesis of InAs nanocrystals in crystalline silicon

The formation of nanodimensional InAs crystallites on Si wafers was studied by the method of high-fluence implantation of As and In ions with subsequent high-temperature treatment. It was found that the size and depth distributions of the crystallites depend on both the implantation temperature and the annealing conditions. A broad band in an energy range of 0.75–1.1 eV was recorded in the photoluminescence spectra of the samples.

Ion implantation enhanced formation of 3C-SiC grains at the SiO2/Si interface after annealing in CO gas

SiC grains can be grown without voids at the SiO2/Si interface using a simple method, i.e. annealing in CO gas. Present experiments aim to create nucleation centers for the SiC crystallite growth by carbon ion implantation. The formation of the nucleation clusters, as well as the morphology, the size and the density of the nanocrystals, were systematically studied by conventional and high resolution Transmission Electron Microscopy. The nanocrystallites were developed following two different modes of growth: The first develops facets along the <100> crystallographic direction giving tetragonal grains, and the second facets along the <110> direction resulting in elongated nanocrystallites. It was shown that combined low dose carbon implantation and subsequent high temperature annealing in CO leads to a substantial increase of the covering of the Si surface by high quality 3C-SiC nanocrystallites.

Hydrogen implantation‐induced large area exfoliation in AlN epitaxial layers

AbstractHydrogen ion implantation in aluminium nitride (AlN) epitaxial layers grown on 2‐inch c‐plane (0001) sapphire substrates was performed with different fluences in the range of 1 × 1017–2 × 1017/cm2 at various implantation temperatures between liquid nitrogen (LN2) to 300 °C. The post‐implantation thermal annealing behaviour of these samples was studied by using optical microscopy, atomic force microscopy (AFM) and transmission electron microscopy (TEM). Our investigations showed that AlN samples that were implanted at LN2 and room temperature (RT) exhibited mostly surface blistering after post‐implantation annealing. On the other hand, the AlN samples that were implanted at 100 and 300 °C showed large area exfoliation of the implanted surface after post‐implantation annealing. The implantation‐induced damage in AlN was analysed by cross‐sectional TEM, which revealed a damage band inside the AlN layer in all the cases that was decorated with hydrogen‐filled nanovoids. These nanovoids showed a greater tendency of agglomerating together to form nanocracks in the as‐implanted state for 100 and 300 °C implanted samples leading eventually to the large area exfoliation after high temperature annealing.

Copper In-Depth Distribution in Hydrogen Implanted Cz Si Wafers Subjected to Two-Step Annealing

In this work we have studied the in-depth distribution of copper deposited on the surface of the hydrogen pre-implanted Cz Si wafers depending on the conditions of their subsequent annealing. In the standard n-type 4.5 ∙cm Cz Si wafers different numbers of radiation defects were formed by hydrogen ion implantation with an energy of 100 keV (0.9 m projected range, Rp) for different fluences (11015, 11016, or 41016 at/cm2) at room temperature. Then a copper layer 50-nm thick was deposited on the sample surface by magnetron sputtering at temperatures 250 or 300 oC with subsequent annealing for 4 h at the same temperatures. Whereupon the surface was chemically etched and the samples were annealed in vacuum during 2 h at 700 oC. The depth profiles of copper in the near-surface layer were controlled by RBS investigations both in the random and channeling modes. These experiments have shown that the copper in-depth distribution strongly depends on the implantation fluence and temperature of the low-temperature annealing: in case of copper deposition at 250 oC a relatively strong peak determined by copper on the surface is observed in RBS spectra after all the above-described steps. On the contrary, for higher temperatures of copper deposition (300 oC) a significant decrease in the intensity of this peak is observed in RBS spectra. A maximal concentration of copper at a depth of the projected range, Rp, was observed for the samples implanted with a maximal fluence (41016 at/cm2).

Structure and Photoluminescence Properties of Ion Beam Synthesized SiC Nanoparticles in Si

Silicon carbide nanoparticles were synthesized in Si(100) wafers by 300 keV C+ ion implantation at elevated substrate temperatures of 550, 650 and 700 degrees C. The implantation has been carried out upto a fluence of 2 x 10(17) ions/cm2 with a constant current density 1.2 microA/cm2. GIXRD analysis on the implanted sample confirms the formation of 3C-SiC. XTEM studies of sample implanted at 650 degrees C show that size of SiC nanoparticles is 6 nm at a depth 0.6 microm from the sample surface. PL spectrum of sample implanted at different temperatures showed a peak at 2.45 eV and 2.3 eV and the intensity of PL peak increases with implantation temperature. The peak at 2.45 eV corresponds to blue shifted emission from SiC nanoparticles having size 6 nm. The peak at 2.3 eV is assigned to the SiC nanoparticles with enhanced d-value.

Infrared surface temperature monitoring in the postoperative management of free tissue transfers.

Early identification of failing free flaps may allow for potential intervention and flap salvage. The predictive ability of flap temperature monitoring has been previously questioned. The present study investigated the ability of an infrared surface temperature monitoring device to detect trends in flap temperature and correlation with anastomotic thrombosis and flap failure. Postoperative measurement of surface temperature was obtained in 47 microvascular free flaps. Differences in temperature between survival and failure groups were evaluated for statistical significance using Student's t test (P<0.05). In addition, a single variable analysis was performed on 30 different flap characteristics to evaluate their prediction of flap failure. In total, eight flaps failed. Five of these were re-explored, of which one was salvaged. The three other flaps died a progressive death secondary to presumed thrombosis of the microcirculation despite adequate Doppler signals. Temperatures of the flap failure group during the last 24 h yielded a mean difference of 2 degrees C (3.56 degrees F) compared with surviving flaps (P<0.05). The temperature of the failing flaps began to decline at the eighth postoperative hour. Single variable analysis identified prior radiation to be a predictor of flap failure. A surface temperature measurement device provides reproducible digital readings without physical contact with the flap. Technical difficulties encountered in previous research with implantable or surface contact temperature probes are obviated with this noncontact technique. Flap temperature monitoring revealed a trend in temperature that correlates with anastomotic thrombosis and eventual flap failure.

Helium implantation into 4H‐SiC

AbstractThe paper provides the properties of single crystalline 4H‐SiC under helium implantation at temperatures of implantation up to 750 °C and fluences in the range 5 × 1015–1 × 1017 cm−2. The microstructure evolution was studied by transmission electron microscopy cross‐section and X‐ray diffraction experiments. The mechanical property changes were investigated by using nanoindentation tests followed by atomic force microscopy observations and by using tribological tests. At elevated temperature of implantation and/or in the low fluence regime at room temperature where only the strained state of SiC is obtained, SiC becomes more resistant to crack formation but no significant change in mechanical properties is seen. At room temperature with increasing fluence the damage accumulation leads to the amorphous state for which a strong degradation of the mechanical properties is observed. At elevated temperature of implantation, amorphization is avoided and a thermally activated saturation of the strain is observed in the near surface region whereas defect accumulation occurs near the maximum of damage. Upon annealing subsequent to room temperature implantation, the near surface strain progressively relaxes while the helium ions agglomerate into platelets around the maximum of strain. These platelets evolve into bubble clusters at temperatures where the vacancies become mobile. Under particular conditions of implantation (high fluence and elevated temperature) the swelling of the surface increases during annealing due to the growth of bubbles and the formation of stacking faults resulting from the migration of interstitials towards the maximum of damage.

Insights into torpor and behavioural thermoregulation of the endangered Juliana's golden mole

AbstractThe cryptic, subterranean ways of golden moles (Chrysochloridae) hamper studies of their biology in the field. Ten species appear on the IUCN red list, but the dearth of information available for most inhibits effective conservation planning. New techniques are consequently required to further our understanding and facilitate informed conservation management decisions. We studied the endangered Juliana's golden mole Neamblysomus julianae and aimed to evaluate the feasibility of using implantable temperature sensing transmitters to remotely acquire physiological and behavioural data. We also aimed to assess potential body temperature (Tb) fluctuations in relation to ambient soil temperature (Ta) in order to assess the potential use of torpor. Hourly observations revealed that Tb was remarkably changeable, ranging from 27 to 33 °C. In several instances Tb declined during periods of low Ta. Such ‘shallow torpor’ may result in a daily energy saving of c. 20%. Behavioural thermoregulation was used during periods of high Ta by selecting cooler microclimates, while passive heating was used to raise Tb early morning when Ta was increasing. In contrast to anecdotal reports of nocturnal patterns of activity, our results suggest that activity is flexible, being primarily dependent on Ta. These results exemplify how behavioural patterns and microclimatic conditions can be examined in this and other subterranean mammal species, the results of which can be used in the urgently required conservation planning of endangered Chrysochlorid species.

Surface Electrical Degradation of Helium Implanted Sapphire

Reliable plasma diagnostic systems are key elements for an efficient and safe operation of future fusion reactors. These systems use particular components, such as ceramic insulators, dielectric and optical windows, optical fibres and complete sensor assemblies. These materials, in addition to neutron and gamma radiation, will be subjected to bombardment by low energy ions and neutral particles. Alumina (Al2O3) is one of the insulating candidate materials to be used in diagnostic systems for ITER, where it will play important roles as electrical insulation and in optical components. Possible material damage has been examined by implanting He into sapphire at different temperatures to simulate ion bombardment. The electrical conductivity in the implanted region increases by more than nine orders of magnitude. Such severe surface electrical degradation is due to the loss of oxygen from the implanted surface. The loss of oxygen also reduces the material band gap in the surface region and as a consequence the optical transmission is severely reduced. Implantation temperature plays an important role, where one observes that although electrical degradation is higher for higher temperature implantation, optical degradation is lower. The electrical conductivity in the implanted region increases by more than nine orders of magnitude. Such severe surface electrical degradation is due to the loss of oxygen from the implanted surface. The loss of oxygen also reduces the material band gap in the surface region and as a consequence the optical transmission is severely reduced. Implantation temperature plays an important role, where one observes that although electrical degradation is higher for higher temperature implantation, optical degradation is lower.

Epitaxial 3C-SiC nanocrystal formation at the SiO2/Si interface by combined carbon implantation and annealing in CO atmosphere

High quality 3C-SiC nanocrystallites were epitaxially formed on (100) Si wafers covered by a 150 nm thick SiO2 capping layer after low dose carbon implantation and high temperature annealing in CO atmosphere. Carbon implantation is used to introduce nucleation sites by forming silicon-carbon clusters at the SiO2/Si interface acting as nucleation sites for the growth of 3C-SiC nanocrystallites. The formation of the nucleation clusters as well as the morphology, the size, and the density of the nanocrystals were systematically studied by conventional and high resolution transmission electron microscopy. The nanocrystallites were developed following two different modes of growth: The first develops facets along the ⟨100⟩ crystallographic direction giving tetragonal grains and the second facets along the ⟨110⟩ direction resulting in elongated nanocrystallites. The formation mechanism of the nanocrystallites and the strain related with them are also discussed.

Raman investigation of hydrogen-implanted and DC hydrogen-plasma-treated Cz Si wafers

The general goal of this work is to demonstrate that the buried defect layer created by hydrogen implantation can serve as a gettering region for hydrogen introduced from a DC plasma and to study the efficiency of this gettering affected by the implantation regimes. Standard n-type 4.5 Ω⋅cm Cz Si wafers were implanted by hydrogen ions with an energy of 100 keV and different doses of 1 × 1014, 1 × 1015, or 5 × 1015 atoms/cm2 at temperatures of 150, 300, 400, or 500 °C. After implantation, hydrogen was introduced to the wafers from the DC plasma at 150 °C. For a comparative estimation of the hydrogen concentration in the wafers implanted in different regimes Raman spectroscopy was used. The peaks of the Raman spectra associated with molecular hydrogen (H2), vacancy-hydrogen (V–H), and silicon–hydrogen (Si–H) complexes were studied depending on the implantation conditions. It is demonstrated that peaks of Raman spectra depend significantly on the dose and temperature of implantation. This means that the concentration of hydrogen in the wafers could be determined from the concentration and type of defects formed by hydrogen implantation. Maximum peaks associated with H2, Si–H, and V–H complexes were observed for the samples implanted at a temperature of 500 °C.

Validation of a totally implantable blood flow, blood pressure and temperature biotelemetry system

The EndoGear totally implantable multichannel biotelemetry system was validated using standard bench‐top instruments. Although this biotelemetry system has already been used in a variety of animal models, it had not been validated over a wider range of heart rates, blood flow velocities, blood pressures and temperatures.Positive displacement pulsatile waveforms were generated using a bellows‐type pump and reference blood flow velocity was measured with a bench‐top Doppler flowmeter (Indus Instruments, 20MHz Doppler flowmeter module), while reference blood pressure was measured with a solid‐state blood pressure catheter (Millar Instruments, model SPR524). Similarly, reference temperature was measured with a calibrated temperature sensor. The pump rate, stroke volume and pressure‐chamber pressure were adjusted to simulate various physiological levels and were recorded on a computer. Temperature was varied separately, in a temperature controlled water bath, and the transmitted temperature data were recorded.The results show that the EndoGear implant is capable of accurately measure flow velocity, pressure and rate waveforms in a large physiological range. This makes it useful in studies where blood flow velocities are in the range of 5‐100 cm/s, blood pressures are in the range of 0 to 300 mmHg, heart rates are up to 250 bpm and temperatures are in the range of 0 to 50°C. The size and weight of this implant allow it to be used in animals with body weights = 2 kg.This research was supported by the Swedish Science Research Council Grants B‐DR 09856‐304 and 621‐2005‐2588