M. Flynn

X-ray-diffraction study of crystalline Si nanocluster formation in annealed silicon-rich silicon oxides

The formation and subsequent growth of crystalline silicon nanoclusters (Si-ncs) in annealed silicon-rich silicon oxides (SRSOs) were studied by glancing angle x-ray diffraction. SRSO samples with Si concentrations (y) of 0.40, 0.42, and 0.45 were grown by inductively coupled plasma-enhanced chemical-vapor deposition (PECVD). Samples with y=0.42 grown by electron-cyclotron-resonance PECVD were also studied. Annealing treatments were performed at temperatures (T) of 900, 1000, and 1100 °C for times (t) between 0.5 and 3 h in flowing Ar. As-grown SRSO films did not present signs of Si clusters (amorphous or crystalline); however, (111), (220), and (311) Bragg peaks corresponding to c‐Si were clearly seen after annealing at 900 °C for the y=0.45 sample, but only barely seen for the y=0.42 and undetected for the y=0.40 samples. For T=1000°C, all studied SRSO samples clearly showed the c‐Si diffraction peaks, which became narrower with increasing t and T. From the width of the Si (111) peaks, the mean size of ...

ZnGa2 O 4 : Mn phosphors for Thin-Film Electroluminescent Displays Exhibiting Improved Brightness

Thin films of ZnGa 2 O 4 :Mn films have been deposited by radio frequency magnetron sputtering in order to study the effects of annealing temperatures less than 1000°C on the thin-film electroluminescent properties. Energy-dispersive X-ray compositional analysis showed a loss of zinc during sputtering, with the film composition being Zn 0.9 Mn 0.03 Ga 2 O 4 . All films showed strong (111) and (222) X-ray reflections relative to the power standard. As the annealing temperature was raised, the texture rotated toward that of the powder material. The as-deposited films showed no photoluminescence; however, once annealed at T ≥ 750°C, a single emission band at 504 nm was observed. Emission wavelength was independent of annealing temperature. The electroluminescent brightness of the devices peaked at an annealing temperature of 900°C. Peak brightness and efficiency were 350 cd/m 2 and 0.55 lm/W at 60 Hz, and 1500 cd/m 2 and 0.30 lm/W at 600 Hz. These high brightness values have been attributed to the roughness of the substrates.

Laser photoluminescence spectrometer based on charge-coupled device detection for silicon-based photonics

We describe and characterize a multichannel modular room temperature photoluminescence spectroscopy system. This low cost instrument offers minimization of size and complexity as well as good flexibility and acceptable spectral resolution. The system employs an efficient flexible front end optics and a sensitive spectrometer with a charge-coupled device array detector. The spectrometer has no moving parts and is more robust than a scanning system. The scientific motivation was to enable the photoluminescence study of various silicon photonics structures. Typical applications are presented for SiOx (x<2) films. It is demonstrated that high-quality steady state photoluminescence data with excellent signal to noise enhancement capability can be delivered besides the ability to perform simultaneous multiwavelength measurements in one shot. This instrument is shown to be useful for evaluating semiconductor wafers, including those intended for light emitting structures from silicon-based photonic crystals. The ...

Silicon nanocrystal formation in silicon-rich silicon oxide thin films

Silicon rich silicon oxide thin films have been fabricated by electron cyclotron resonance plasma enhanced chemical vapor deposition. Following their deposition, these films were subjected to thermal anneals at temperatures up to 1100°C for times of up to 120 minutes. Annealing of the films causes a phase separation of the material to form Si precipitates, which nucleate to form Si nanocrystals, within an amorphous SiO2 matrix. The nucleation of the nanocrystals was analyzed as a function of the composition of the films, as determined by Rutherford backscattering and elastic recoil detection analysis experiments, and the annealing conditions. The bonding structure of the films was analyzed using Fourier transform infrared spectroscopy. Surface morphology, including analysis of the size and distribution of the nanocrystals, was determined through the use of atomic force microscopy. Spectroscopic ellipsometry, in the range from 600 to 1100 nm, was used to examine the effects of the formation of nanocrystals on the optical properties, i.e., index of refraction and extinction coefficient, of the films. Photoluminescence spectra were used to show that due to quantum confinement effects the nanocrystals exhibit luminescence, making them a potential candidate for integrated photonic emitters.

Sputtered Zn1−xGa2O4:Mn thin-film electroluminescent devices prepared using cadmium-assisted processing

Incorporating cadmium in the sputtering targets used to grow green-emitting zinc gallate doped with manganese is found to provide improvements in crystallinity, photoluminesience (PL), and electroluminescence (EL) performance, while reducing the annealing temperature requirements. It is shown that as-grown thin films do contain cadmium. The cadmium is then lost during thin-film annealing. The effect of cadmium is interpreted as an enhancement in vacancy concentration during the thin-film annealing process, which improves crystallinity, EL, and PL. X-ray diffraction and microscopy results are carefully studied and discussed.

The Impact of the Rare-earth Precursor on the Composition, Structure and Luminescence of Er-doped Silicon-rich Silicon Oxide Films

Silicon-rich silicon oxide films have been doped using an organometallic erbium precursor. Carbon contamination in the films is shown to have a pronounced effect on the visible photoluminescence. The doping also impacts formation of nanocrystals within the films

Compositional and optical characterization of SiO/sub x/ films deposited by ECR-PECVD for photonics applications

Thin SiO/sub x/ films were deposited using ECR-PECVD. The composition and structure of the samples was determined using Rutherford backscattering and Fourier transform infrared spectroscopy while photoluminescence and ellipsometric measurements were used to characterize the samples optically. AFM measurements confirmed the presence of silicon nanocrystals after annealing the samples. These materials have the potential to he used in a variety of applications, including rare-earth doping, as well as their applicability to optical coatings because of the large achievable range of refractive indices.