U.S. Sias

Optical and structural properties of Si nanocrystals produced by Si hot implantation

It was already demonstrated that Si hot implantation followed by high-temperature annealing induces the formation of Si nanocrystals (Si NCs) which when excited in a linear excitation regime present two photoluminescence (PL) bands (at 780 and 1000 nm). We have undertaken the present work in order to investigate three features: First, to determine the origin of each band. With this aim we have changed the implantation fluence and the high-temperature annealing time. Second, to investigate the influence of the postannealing atmosphere on the PL recovering process after bombarding the Si NCs. Third, we have annealed the as-produced Si NCs in a forming gas (FG) atmosphere in order to observe the PL behavior of each band. The results have shown that the 780 nm PL band has its origin in radiative interfacial states, while the 1000 nm one is due to quantum size effects. From the experiments we have concluded that the PL recovery after the Si NCs irradiation strongly depends on the type of postannealing atmosphe...

Photoluminescence behavior of Si nanocrystals as a function of the implantation temperature and excitation power density

In this work we present a study of photoluminescence (PL) on Si nanocrystals (NC) produced by ion implantation on SiO2 targets at temperatures ranging between room temperature and 800°C and subsequently annealed in N2 atmosphere. The PL measurements were performed at low excitation power density (20mW∕cm2) in order to avoid nonlinear effects. Broad PL spectra were obtained, 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. In addition we have studied the PL dependence on the excitation power density (from 0.002to15W∕cm2). The samples with broad NC size distribution containing large grains, as reveal...

Photoluminescence from Si nanocrystals induced by high-temperature implantation in SiO2

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.

Polymer thermal protection induced by ion beam irradiation

Abstract The thermal stability of F, Ne, He, and B implanted/irradiated AZ1350-J photoresist films has been investigated via the Rutherford backscattering (RBS) technique. We find that both shallow and deep implantations raise the temperature at which the photoresist starts to decompose (from 400°C to 450°C). It is shown that radiation rather than chemical effects are responsible for the improvement in the thermal behavior of the implanted/irradiated films. In addition it is observed that the deep implantations give better results as compared with the shallow ones. In fact after a high energy Ne, B or He irradiation fluence was reached, no material loss was observed when the samples were further submitted to 450°C annealings. This is at variance with what was observed with shallow F and Ne implantations, where only partial protection was achieved.

POLYMER THERMAL STABILITY ENHANCEMENT INDUCED BY HIGH ENERGY ION BEAM BOMBARDMENT

Abstract The thermal stability of high energy Ne, He, and B irradiated AZ1350-J photoresist films has been investigated via the Rutherford Backscattering Technique (RBS). We find that as consequence of the irradiations the temperature at which the photoresist starts to decompose raises from 400°C to 450°C. This feature is achieved only when a threshold fluence is implanted, being this value function of the implanted ion. However, the corresponding threshold energy density transfer is similar for all the ions and of the order of 10 eV/A3.

Electroluminescence induced by Ge nanocrystals obtained by hot ion implantation into SiO2

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 Φ=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.