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A systematic study of photoluminescence (PL) behavior of Si nanocrystals in SiO2 obtained by ion implantation in a large range of temperatures (-200 up to 800 °C), and subsequent furnace annealing in N2 ambient was performed. A PL signal in the wavelength range 650–1000 nm was observed. The PL peak wavelength and intensity are dependent on the fluence, implantation and annealing temperatures. It was found that after annealing at 1100 °C, both implantations of 1.5×1017 Si/cm2 at room temperature or 0.5×1017 Si/cm2 at 400 °C result in the same PL peak intensity. By varying the implantation temperature we can achieve the same PL efficiency with lower fluences showing that hot implantations play an important role for initial formation of the nanocrystals. The PL intensity evolution as a function of the annealing time was also studied. As the implantation temperature was increased, larger mean size Si nanocrystals were observed by means of dark-field transmission electron microscopy analysis. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Focuses on a study which detailed the depth profile and thermal annealing behavior of bismuth implanted into an Al/Ti bilayer structure. Factor that acts as a diffusion barrier for bismuth; Motive for performing ion implantation; Cause of the discontinuous change in the implanted range profile at the interface.

Commonly, electroluminescence (EL) from Ge nanocrystals (Ge NCs) has been obtained by room temperature (RT) Ge implantation into a SiO2 matrix followed by a high temperature anneal. In the present work, we have used a novel experimental approach: we have performed the Ge implantation at high temperature (Ti) and subsequently a high temperature anneal at 900 °C in order to grow the Ge NCs. By performing the implantation at Ti=350 °C, the electrical stability of the MOSLEDs were enhanced, as compared to the ones obtained from RT implantation. Moreover, by changing the implantation fluence from [uppercase_phi_synonym]=0.5×1016 and 1.0×1016 Ge/cm2 we have observed a blueshift in the EL emission peak. The results show that the electrical stability of the hot implanted devices is higher than the ones obtained by RT implantation. [ABSTRACT FROM AUTHOR]

Commonly, electroluminescence (EL) from Ge nanocrystals (Ge NCs) has been obtained by room temperature (RT) Ge implantation into a SiO2 matrix followed by a high temperature anneal. In the present work, we have used a novel experimental approach: we have performed the Ge implantation at high temperature (Ti) and subsequently a high temperature anneal at 900 °C in order to grow the Ge NCs. By performing the implantation at Ti=350 °C, the electrical stability of the MOSLEDs were enhanced, as compared to the ones obtained from RT implantation. Moreover, by changing the implantation fluence from [uppercase_phi_synonym]=0.5×1016 and 1.0×1016 Ge/cm2 we have observed a blueshift in the EL emission peak. The results show that the electrical stability of the hot implanted devices is higher than the ones obtained by RT implantation. [ABSTRACT FROM AUTHOR]

We report on Raman spectroscopy, temperature-dependent in-plane resistivity, and in-plane magnetoresistance experiments in highly oriented pyrolytic graphite (HOPG) implanted with As and Mn. A pristine sample was also studied for comparison. Two different fluences were applied, $$\varphi = 0.5\times 10^{16}\,\, {\hbox {ions}}/{\hbox {cm}}^{2}$$ and $$\varphi = 1.0\times 10^{16}\,\,{\hbox {ions}}/{\hbox {cm}}^{2}$$ . The implantations were carried out with 20 keV ion energy at room temperature. The Raman spectroscopy results reveal the occurrence of drastic changes of the HOPG surface as a consequence of the damage caused by ionic implantation. For the higher dose, the complete amorphization limit is attained. The resistivity and magnetoresistance results were obtained placing electrical contacts on the irradiated sample surface. Owing to the strong anisotropy of HOPG, the electrical current propagates mostly near the implanted surface. Shubnikov-de Haas (SdH) oscillations were observed in the magnetoresistance at low temperatures. These results allow the extraction of the fundamental SdH frequencies and the carriers' effective masses. In general, the resistivity and magnetoresistance results are consistent with those obtained from Raman measurements. However, one must consider that the electrical conduction in our samples occurs as in a parallel association of a largely resistive thin sheet at the surface strongly modified by disorder with a thicker layer where damage produced by implantation is less severe. The SdH oscillations do not hint to significant changes in the carrier density of HOPG. [ABSTRACT FROM AUTHOR]

Presents information on a study which determined the depth distribution of ion-implanted [sup10]boron in AZ111 photoresist in the 30-150 kiloelectrovolts energy range. Aspects of ion-implanted and irradiated polymers; Experimental procedure; Results and discussion; Conclusions.

Abstract: In this work, SiO2 layers containing Ge nanocrystals (NCs) obtained by the hot implantation approach were submitted to an ion irradiation process with different 2MeV Si+ ion fluences. We have investigated the photoluminescence (PL) behavior and structural properties of the irradiated samples as well as the features of the PL and structural recovery after an additional thermal treatment. We have shown that even with the highest ion bombardment fluence employed (2×1015 Si/cm2) there is a residual PL emission (12% from the original) and survival of some Ge NCs is still observed by transmission electron microscopy analysis. Even though the final PL and mean diameter of the nanoparticles under ion irradiation are independent of the implantation temperature or annealing time, the PL and structural recovery of the ion-bombarded samples have a memory effect. We have also observed that the lower the ion bombardment fluence, the less efficient is the PL recovery. We have explained such behavior based on current literature data. [Copyright &y& Elsevier]

Abstract: In the present paper we report structural and photoluminescence (PL) results from samples obtained by Si implantation into stoichiometric silicon nitride (Si3N4) films. The Si excess was introduced in the matrix by 170keV Si implantation performed at different temperatures with a fluence of Φ=1×1017 Si/cm2. The annealing temperature was varied between 350 and 900°C in order to form the Si precipitates. PL measurements, with a 488nm Ar laser as an excitation source, show two superimposed broad PL bands centered around 760 and 900nm. The maximum PL yield is achieved for the samples annealed at 475°C. Transmission electron microscopy (TEM) measurements show the formation of amorphous nanoclusters and their evolution with the annealing temperature. [Copyright &y& Elsevier]

Some hydrophilic transformations in polyhydroxyalkanoates were assessed in this study. It was proved that polyhydroxybutyrate-graft-polyvinylacetate copolymers are more hydrophilic than polyhydroxybutyrate and exhibit a strong dependence between hydrophilicity and polyvinylacetate content in the copolymers. Water wettability of some polyhydroxyalkanoates was improved by H+ (300 keV, flux ranging from 1011 to 5 × 1013 ions/cm2), Ag+ (20 keV, fluences ranging from 1014 to 1016 ions/ cm2), and Na+ (25 and 12.5 keV to 5 × 1015 ions/cm2) implantation experiments. Additionally, surface properties were characterized by means of water drop contact angle, atomic force microscopy, X-ray diffraction, and infrared spectroscopy. The influence of surface morphology on the wettability was discussed. [ABSTRACT FROM PUBLISHER]

The diffusion of nitrogen in α-Hf was studied in the temperature range of (823–1123) K using the ion implantation and nuclear resonance techniques. The measurements show that the diffusion coefficients follow the Arrhenius behavior D( T)= D0exp (− Q/ RT) with D0=(5.5±2.1)×10−7 m2/s and Q=(228±1) kJ/mol. A comparison of the present results with the previous one is done. [ABSTRACT FROM AUTHOR]

Abstract: Si nanocrystals (Si NCs) produced by hot implantation present two photoluminescence (PL) bands (at 780 and 1000nm, respectively) when measured at low pump power (∼20mW/cm2). Since each PL band was shown to have different origin we have investigated the passivation effect on them, as well as their PL decay lifetime. PL and time resolved PL measurements have demonstrated that both PL bands present different behavior after the passivation process. We have found that only the 1000nm PL band is strongly influenced by the passivation process in its intensity as well as in its decay lifetime. In addition we have studied samples implanted at 600°C annealed at 1150°C for different time intervals and further passivated. The results show that the passivation effect on the 1000nm PL band is strongly dependent on the preannealing time. [Copyright &y& Elsevier]

Abstract: We report an investigation on the effect of the fluence and annealing time on the photoluminescence (PL) from Si nanocrystals produced by hot implantation of Si into a SiO2 matrix followed by thermal treatment in nitrogen. We have varied the implantation fluence in a wide range, from 0.35×1017 to 4×1017 Si/cm2. In addition, the PL evolution with the annealing time (1 up to 15h) was studied for the samples implanted with fluences between 1×1017 and 4×1017 Si/cm2. After annealing the spectra present two PL bands: one centered at 780nm and a second one around 1000nm. The influence of the studied parameters on the PL behavior of both bands suggests different origins for their emission. The results are discussed in terms of current models. [Copyright &y& Elsevier]

The diffusion of 18O in α-Tiwas studied in the 623–873 K temperature range by using the ion implantation and nuclear resonance techniques. The measurements show that the diffusion coefficients follow an Arrhenius behavior with diffusion parameters D0=(2±1)10-7 m2 s-1 and Q=(±) 16950kJ/mol, values typical of interstitial diffusion mechanism. A comparison of the present and previous results is also done. [ABSTRACT FROM AUTHOR]

100-keyV 10B+ ions were implanted into photoresist in different directions at a fluence of 1X10[SUP14] cm[SUP-2], and their depth distribution was determined by means of the neutron depth profiling technique. In no case were the projectile ions found to come to rest according to their predicted implantation profiles. Instead, they are always found to undergo considerable long-range migration. During the irradiation process this motion appears to he enhanced by the radiation damage, and during the subsequent annealing steps one deals with thermal diffusion , The implant redistribution is always found to be governed strongly by the self-created damage, insofar as both electronic and nuclear defects in the polymer act as trapping centers, The implant redistribution shows a pronounced directional dependence, essentially as a consequence of the spatial distribution of the electronic energy loss, The changes of the nuclear defect distribution during thermal annealing are studied by a specially developed tomographic method in three dimensions. [ABSTRACT FROM AUTHOR]

[sup 6] Li[sup +] (150 keV) was implanted into thin polypropylene foils at fluences of 1×10[sup 13] to 1×10[sup 14] cm[sup -2] . Subsequent neutron depth profiling measurements of the Li distributions revealed considerable deviations from the expected ballistic range profiles. This Li redistribution was simulated by a numerical computer calculation. The best fit between measurements and simulations was obtained by assuming that (i) Li redistributes immediately after its ballistic slowing-down, (ii) the Li mobility is enhanced in the radiation-damaged polymer region, the local diffusion enhancement being controlled by the target’s electronic damage, (iii) mobile Li is readily trapped at radiation-induced defects, their density being proportional to the target’s electronic damage, (iv) these traps are saturable ones, and (v) Li migration is not restricted to the ion track region, but proceeds also through the neighboring unirradiated bulk, though with slower speed. [ABSTRACT FROM AUTHOR]

Abstract: Up to the present, by using the ion implantation technique, photoluminescence (PL) from Ge nanocrystals (Ge NCs) was obtained by room temperature (RT) Ge implantation into a SiO2 matrix followed by a high temperature anneal. In this way two PL bands were observed, one at 310nm and the second, with much higher yield at 390nm. In the present work we have used another experimental approach. We have performed the Si implantation at high temperature (T i) and then, we have done a higher temperature anneal (T a) in order to nucleate the Ge NCs. With this aim we have changed T i between RT and 600°C. By performing the implantation at T i =350°C we found a PL yield four times higher than the one obtained from the usual RT implantation at the same fluence. Moreover, by changing the implantation fluence between Φ =0.25×1016 and 2.2×1016 Ge/cm2 we observed that Φ =0.5×1016 Ge/cm2 induces a PL yield three times higher as compared to the usual RT implantation fluence. In conclusion, using a hot Ge implantation plus an optimal Ge atomic concentration, we were able to gain more than one order of magnitude in the 390nm PL yield as compared with previous ion implantation results. [Copyright &y& Elsevier]

Abstract: Up to the present, photoluminescence (PL) was obtained from near stoichiometric or amorphous Si nitride films (SiN x ) after annealing at high temperatures. As a consequence, the existence of PL bands has been reported in the 400–900nm range. In the present contribution, we report the first PL results obtained by Si implantation into a stoichiometric 380nm Si3N4 film. The Si excess is obtained by a 170keV Si implantation at different temperatures with a fluence of Φ =1017 Si/cm2. Further, we have annealed the samples in a temperature range between 350 and 900°C in order to form the Si precipitates. PL measurements were done using an Ar laser as an excitation source, and a broad PL band basically centered at 910nm was obtained. We show that the best annealing condition is obtained at T a =475°C for the samples implanted at 200°C, with a PL yield 20% higher than the obtained at room temperature implantation. Finally, we have varied the implantation fluence and, consequently, the Si nanocrystals size. However, no variation was observed nor in the position neither in the intensity of the PL band. We concluded that the PL emission is due to radiative states at the matrix and the Si nanocrystals interface, as previously suggested in the literature. [Copyright &y& Elsevier]

The diffusion of 15N in α-Ti was studied in the 673–1023 K temperature range by using the ion implantation and nuclear resonance techniques. The measurements show that the diffusion coefficients follow an Arrhenius behavior D(T)=D0 -Q/RT, where D0=(1.1±0.8)×10-7 m2 s-1 and Q=(183±2) kJ/mol. A comparison with previous results is also given. [ABSTRACT FROM AUTHOR]

He[sup +] ions were implanted at 40 keV into Si <100> channel direction at room temperature (RT) and at 350 °C. The Si samples were subsequently doped with Cu in order to study the gettering of Cu atoms at the defective layer. A subsequent annealing at 800 °C was performed in order to anneal the implantation damage and redistribute the Cu into the wafer. The samples were analyzed by Rutherford backscattering channeling and transmission electron microscopy techniques. The Cu distribution was measured by secondary ion mass spectrometry (SIMS). The SIMS experiments show that, while the 350 °C implant induces gettering at the He projected range (R[sub p]) region, the same implant performed at RT has given as a result, gettering at both the R[sub p] and R[sub p]/2 depths. Hence, this work demonstrates that the R[sub p]/2 effect can be induced by a light ion implanted at low energy into channeling direction. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: The present work deals with the photoluminescence (PL) emitted from Eu and Tb ions implanted at room temperature (RT) up to 350°C in a SiO2 matrix, followed by a further anneal process. The ions were implanted with energy of 100keV and a fluence of 3×1015 ions/cm². Further anneals were performed in atmospheres of N2 or O2 with temperatures ranging from 500 up to 800°C. PL measurements were performed at RT and structural measurements were done via transmission electron microscopy (TEM). In addition, the Rutherford backscattering technique (RBS) was used to investigate the corresponding ion depth profiles. For Tb, the optimal implantation temperature was 200°C, and the anneal one was of 500°C. Under these conditions, the PL yield of the sharp band centered at 550nm was significatively higher than the one obtained with RT implants. The PL spectra corresponding to the Eu ions show two bands, one narrow centered around 650nm and a second broad one in the blue–green region. The implantation temperature plays a small influence on the PL shape and yield. However, the annealing atmosphere has a strong influence on it. Samples annealed in N2 present a broad PL band, ranging from 370 up to 840nm. On the other hand, the O2 anneal conserves the original as-implanted spectrum, that is: a broad PL band in the blue–green region together with sharp PL band in the red one. For both ions, Tb and Eu, the TEM analyses indicate the formation of nanoclusters in the hot as-implanted samples. [Copyright &y& Elsevier]

Abstract: In the present work we have studied the photoluminescence (PL) behavior from Si nanocrystals (NCs) as a function of the excitation power density and annealing time. The NCs were produced in a SiO2 matrix by Si implantations from room temperature (RT) up to 700°C, followed by post-annealing in N2 atmosphere at high temperature. With this aim we have changed the excitation power density (from 2×10−3 W/cm2 up to 15W/cm2) and the annealing time (from 10min up to 15h). The strong PL signal, which at 15W/cm2 is composed by a single-peak structure (650–1000nm) centered at around 780nm, expands up to 1200nm showing a two-peak structure when measured at 20×10−3 W/cm2. The peak structure located at the short wavelength side is kept at ∼780nm, while the second peak, starting at around 900nm, redshifts and increases its intensity with the implantation temperature and annealing time. The effect of the annealing time on the PL spectra behavior measured at low excitation power agrees by the first time with the Si NC growth according to quantum confinement effects. [Copyright &y& Elsevier]

Abstract: In this work we present a photoluminescence (PL) study on Si nanocrystals produced by ion implantation on SiO2 targets at temperatures ranging between 25 and 800°C and subsequently annealed in N2 atmosphere. The PL measurements were performed at low excitation power (20mW/cm2) in order to avoid nonlinear effects. Broad PL spectra were obtained (from 650 up to 1050nm), presenting a line shape structure that can be reproduced by two superimposed peaks at around 780 and 950nm. We have observed that both PL intensity and line shape change by varying the annealing as well as the implantation temperatures. Implantations performed at 400°C or higher produce a remarkable effect in the PL line shape, evidenced by a strong redshift, and a striking intensity increase of the peak located at the long wavelength side of the PL spectrum. [Copyright &y& Elsevier]

100 keV 6Li+ ions were implanted into polystyrene at fluences of 1 × 1013 to 1 × 1014 cm−2, and their depth distributions were determined by means of the neutron depth profiling technique. In no case the projectile ions are found to come to rest according to their predicted implantation profiles. Instead, they always undergo considerable migration. During the irradiation process this motion is influenced by the radiation damage, and during the subsequent annealing steps one deals with thermal diffusion. The implant redistribution is always found to be governed strongly by the self-created damage, insofar as both electronic and nuclear defects in the polymer act as trapping centers. [Copyright &y& Elsevier]

We report experimental results on the formation of He bubbles in Cz grown (1 0 0) Si crystals implanted with 40 keV He+ ions to a fluence of 1×1016 cm−2 at distinct implantation temperatures within the 373&les;Ti&les;573 K range, and upon 600 s post-implantation thermal annealings at temperatures from 673 to 1073 K. The samples were analyzed by Rutherford backscattering/channeling spectrometry, elastic recoil detection analysis and transmission electron microscopy. The results obtained show that the microstructure characteristics of the bubble systems, as well as their thermal evolution behavior, depend significantly on the implantation temperature. A correlation between the dynamic annealing behavior and the bubble formation process is proposed. [Copyright &y& Elsevier]

A systematic study of photoluminescence (PL) behavior of Si nanocrystals in SiO2 obtained by ion implantation in a large range of temperatures (-200 up to 800 °C), and subsequent furnace annealing in N2 ambient was performed. A PL signal in the wavelength range 650–1000 nm was observed. The PL peak wavelength and intensity are dependent on the fluence, implantation and annealing temperatures. It was found that after annealing at 1100 °C, both implantations of 1.5×1017 Si/cm2 at room temperature or 0.5×1017 Si/cm2 at 400 °C result in the same PL peak intensity. By varying the implantation temperature we can achieve the same PL efficiency with lower fluences showing that hot implantations play an important role for initial formation of the nanocrystals. The PL intensity evolution as a function of the annealing time was also studied. As the implantation temperature was increased, larger mean size Si nanocrystals were observed by means of dark-field transmission electron microscopy analysis. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report on magneto-transport experiments in a high-quality sample of highly-oriented pyrolytic graphite (HOPG). Magneto-resistance and Hall resistivity measurements were carried out in magnetic inductions up to B = 9 T applied parallel to the c -axis at fixed temperatures between T =2 K and T =12 K. The sample was submitted to three subsequent irradiations with As ions. The implanted As contents were 2.5, 5 and 10 at% at the maximum of the distribution profile. Experiments were performed after each implantation stage. Shubnikov-de Haas (SdH) oscillations were observed in both the magneto-resistance and Hall-effect measurements. Analyses of these results with fast Fourier transform (FFT) lead to fundamental frequencies and effective masses for electrons and holes that are independent of the implantation fluences. The Hall resistivity at low temperatures shows a sign reversal as a function of the field in all implanted states. We interpret the obtained results with basis on a qualitative model that supposes the existence of an extrinsic hole density associated to the defect structure of our sample. We conclude that the As implantation does not produce a semiconductor-type doping in our HOPG sample. Instead, an increase in the extrinsic hole density is likely to occur as a consequence of disorder induced by implantation. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, we have studied the photoluminescence (PL) and decay lifetime of Tb and Eu nanoparticles (NPs) at low temperatures. The NPs were obtained by ion implantation into a SiO2 matrix. Concerning the PL emission of Tb NPs (from 370 to 700nm), the shape does not change with the sample temperature and the PL yield has a maximum at 12K and decreases with increasing temperature, reaching a minimum at 300K. The PL lifetime is wavelength independent and remains almost constant at a value of 1.5ms. Regarding Eu NPs emission, two spectral regions were identified, one with narrow emission bands (from 570 to 750nm) and the other with a broad emission band (from 400 to 550nm). Both PL regions show a minimum yield at 12K, and next it rises with increasing temperatures, reaching the maximum at around 100K. Then, the PL yields start to decrease, reaching at 300K a value similar to the one obtained at 12K. For the Eu NPs PL lifetime, two different results were obtained. The long wavelength spectral region shows a lifetime of the order of 1.0ms independent of the temperature. Conversely, the short wavelength one is strongly temperature dependent, being of the order of several milliseconds for temperatures lower than 100K down to 0.05ms at 300K. [Copyright &y& Elsevier]

Abstract: As part of the studies of new materials to be used as electrodes for plasma torches, polycrystalline copper thin film substrates, obtained by depositing copper on silicon wafer using the Electron Beam technique, were implanted with low energy (20–50 keV) alkali ions. The samples, before and after implantation process, were analysed in terms of surface composition and work function changes. Although the implantation doses were low (3×1015 ions/cm2), relatively high concentrations of alkali metals were detected on the surface, which yielded a work function decrease of 3–9% in relation to the copper value. [Copyright &y& Elsevier]

Photoluminescence (PL) of Si nanocrystals embedded in SiO2 was systematically studied by changing Si fluence, implantation temperature (−200 up to 800 °C) and post-annealing temperature. PL signal in the wavelength range 650–1000 nm was observed after annealing. We have observed that the PL intensity and spectra shape are dependent on the implantation temperature. A PL peak redshift is observed when this temperature is increased. Same PL intensity was achieved with fluence three times lower by implanting Si at 400 °C than at room temperature. From our results we have confirmed that implantations at 400 °C or higher play an important role facilitating the crystallites growing process during posterior annealing at high temperature. [Copyright &y& Elsevier]