bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vapor Deposition of Parylene Films from Precursors
Authors: You L. , Yang G.-R. , Lang C.-I. , Wu P. , Moore J. A. , McDonald J. F. , Lu T.-M. 
Published: March 2011

ABSTRACTParylene films, depending on the type, are thermally stable up to 530°C and have low dielectric constants ranging from 2.35 to 3.15. One of the most interesting properties of this material is its vapor depositability. Conventional vapor deposition involves cracking the parylene dimers at temperatures from 600 to 730 °C and polymerizingthe monomers at - 35 °C to RT. We have developed a simpler and less expensive technique that directly uses the precursors from which the dimers are made. This method requires the use of metal catalysts to produce parylene films. We have used the precursors α,α'-dibromo-p-xylene and dibromotetrafluoro-p-xylene to produce N-type and F-type parylene films. FTIR, XPS, thermal stability, and electrical studies show that the F-type parylene films grown from the precursors are comparable to, or sometimes better than, the films grown from dimer, and have potential microelectronics applications.
Mechanism of Reactive Ion Etching of Polymeric Films in Oxygen-Based Plasmas
Authors: Graham Sandra W. , Steinbrüchel Christoph 
Published: March 2011

ABSTRACTThe etching of polymeric films in O2 plasmas containing small amounts of CF4 has been studied at low pressures (10–60 mtorr) in an RIE reactor. The relationship between etch rate, ion flux, and O atom concentration is investigated for photoresist, polyimide, and amorphous carbon. The applicability of a surface-chemical model proposed by Joubert, et al. (J. Appl. Phys. 65(12) 1989, 5096) is explored. Modifications to the model are made to include physical sputtering and direct reactive ion etching. The modified model provides an improved description of the process, showing the various contributions of the ions and O atoms to the overall etching.
Synthesis, Characterization and Evaluation of Zinc-Amides as Potential Dopant Sources for ZnSe OMVPE
Authors: Rees William S. , Green David M. , Hesse Werner , Anderson Timothy J. , Pathangey Balu 
Published: March 2011

ABSTRACTCompounds of the general forms Zn[N(R)2]2, Zn(N(R)(R')2] and Zn{[N(R)2][N(R')2]} have been prepared, these new compositions have been characterized by multinuclear NMR, GC/MS, FTIR, elemental analysis and single crystal x-ray diffraction, and they have been evaluated for their potentialto serve as “designer dopants” in the epitaxial growth of p-type ZnSe. Retention of the Zn-N bond during deposition should insure selective location of the nitrogen atom on the native selenium lattice site. Precursor vapor pressures, vapor phase decomposition mechanisms, and thin film properties are presented. Results from materials characterization by XRD, SIMS, PL, Raman and SEM are presented in the context of evaluating dopantlevel.
Low-Temperature Deposition of ZrC thin films from a Single-Source Precursor
Authors: Smith David C. , Rubiano Rodrigo R. , Healy Matthew D. , Springer Robert W. 
Published: March 2011

ABSTRACTStable zirconium carbide thin films have been deposited from a singlesource organometallic precursor, tetraneopentyl zirconium, at substrate temperatures above 500 °C. Materials deposited above this temperature are crystalline by X-ray diffraction. A metal to carbon ratioof 1:2 is observed by Auger electron spectroscopy depth profiling. X-ray photoelectron spectroscopy indicates the zirconium is single phase. The observed spectra correspond well to spectra for zirconium carbide standards. Carbon XPS reveals carbidic and graphitic or hydrocarbon species with a third unknown carbon species. Elastic recoil detection finds a large, up to 16%, hydrogen content in the thin film.
The Realization of Molecular Control Over Solid State Structure: Chemical Vapor Deposition of Gallium and Indium Sulfide Films
Authors: Power Michael B. , Macinnes Andrew N. , Hepp Aloysius F. , Barron Andrew R. 
Published: March 2011

ABSTRACTThe chemical vapor deposition of cubic gallium sulfide and tetragonalindium sulfide films is reported. The structure of the deposited films was demonstrated to be defined not solely by thermodynamics, but bythe predesigned molecular motif of the precursor molecules. Analysis of the deposited films has been obtained by transmission electron microscopy (TEM), with associated energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS).
Single Source Precursors for the Growth of Metal-Chalcogenide Thin Films
Authors: Seligson Allen L. , Bonasia Philip J. , Arnold John , Yu Kin-Man , Walker Jim M. , Bourret Edith D. 
Published: March 2011

ABSTRACTWe have recently reported the growth of ZnTe and CdTe thin films from the novel volatile single-source precursors Zn(sitel)2 and Cd(sitel)2 [sitel = TeSi(TeSi(siMe3)3]. In an effort to understand the role played by the bulky substituents, we have prepared a number of related compounds and have investigated their potential for the growth of II-VI materials. We now describe the synthesis and characterization of M[EX(SiMe3)3]2 (M = Zn, Cd, Hg for E = Te, X = C; M = Zn for E = Se, X = C, Si) and their use as precursors molecules for the growth of ZnSe, ZnTe, CdTe and HgTe. The thin films were characterized by Rutherford Back scattering spectrometry (RBS) and X-ray diffraction. Pyrolysis reaction conditions for the alkyl and silyl chalcogenolates are also compared.
Samarium Monosulfide Films Prepared from Organometallic Compounds
Authors: Zavyalova L. V. , Domrachev G. A. , Suvorova O. N. , Shupak E. A. , Svechnikov G. S. 
Published: March 2011

ABSTRACTThe possibility of preparation SmS films by the chemical method from organic compounds has been studied. For this purpose three types of coordinatively-saturated compounds based on dithiocarbamate complexes were synthesized and studied by various methods.
Alkoxide Doping of GaAs During Organometallic Vapor Phase Epitaxy
Authors: Park Y. , Skowronski M. , Rosseel T. M. 
Published: March 2011

ABSTRACTDoping of GaAs with dimethylaluminum methoxide and its effects have been studied during metalorganic vapor phase epitaxy. Oxygen concentration decreases exponentially with increasing growth temperature and the activation energy equal to 1.8 eV.Increase of oxygen content with decrease of V/III ratio indicates that oxygen most likely occupies arsenic site. Photoluminescence intensity was observed to decrease with increasing oxygen contentand three new deep level luminescence peaks appeared at 75, 96, and 160 meV below the band gap. This, together with the fact that as-grown layers are fully depleted, indicates that oxygen is electrically active in OMVPE GaAs and forms deep non-radiative recombinationcenters.
Visible Light Emission from Porous Silicon Examined by Photoluminescence and Raman Spectroscopy
Authors: Guilinger Terry R. , Kelly Michael J. , Tallant David R. , Redman David A. , Follstaedt David M. 
Published: March 2011

ABSTRACTWe describe the acquisition of Raman and photoluminescence (PL) spectra on porous silicon (PS) samples that emit visible light. Spectra were acquired in both ex situ experiments (after exposure to air) and in situ experiments (with the PS covered either with the hydrofluoric acid electrolyte used in the formation process or water). Our results generally show a correlation of blue-shifted PL with increased oxidation. In one set of ex situ experiments, however, we observed an inconsistency in the shift of the wavelengthof maximum luminescence intensity for PS samples that exhibit oxygenated character in the Raman spectra. A higher anodization current density produced a red shift in the PL spectra in one experiment, while chemical dissolution of the PS by hydrofluoric acid produced the well-known blue shift in the other case. In two in situ experiments, we observed very weak and red-shifted PL for a PS sample immersed in HF (compared to the same sample measured later in air) while in another we immersed air-exposed PS in water and observed a 15-fold increase in PL intensity along with a blue shift in the luminescence maximum.
Luminescence Properties of Porous Silicon
Authors: Peng C. , Tsybeskov L. , Fauchet P. M. 
Published: March 2011

ABSTRACTWe report the results of a systematic study of the influence of the anodization and etching conditions, and chemical and thermal treatments on the properties of light-emitting porous silicon (PSI). PSI layers with stable, high efficiency photoluminescence (PL) tunable from the near infrared to the yellow have been obtained using p-type and n-type substrates. As the temperature drops below 100 K, the as-anodized PSI layers display striking changes in the PL spectra, which are absent in PSI layers that have received a post-growth treatment.
The Luminescence Mechanism of Porous Silicon
Authors: Calcott P. D. J. , Nash K. J. , Canham L. T. , Kane M. J. , Brumhead D. 
Published: March 2011

ABSTRACTWe report resonantly excited photoluminescence (PL) spectroscopy of highly porous silicon. In the PL spectra we observe satellite structure due to the participation of momentum-conserving phonons in the optical transitions. The momentum-conserving role of these phonons, together with their energies and relative coupling strengths, demonstrate beyond doubt that crystalline silicon, which has already been shown to be the dominant constituent of unoxidised porous silicon, also forms the luminescent material. We show that the theory of quantum confinement in crystalline silicon wires can explain our results and those of other experiments, if the electron-hole interaction, andthe localisation of carriers by fluctuations in wire width, are taken into account.
Optical Properties and New Functionality of Nanocrystalline CuCl and Ge
Authors: Masumoto Yasuaki 
Published: March 2011

ABSTRACTLasing of nanocrystalline CuCl embedded in a NaCl single crystal wasobserved for the first time. Lasing takes place at 77 K in nanocrystalline CuCl sandwiched between dielectric mirrors under the pulsed ultraviolet laser excitation. The lasing transition is that from bi-exciton to exciton. The lasing is observed up to 108 K. The optical gain of nanocrystalline CuCl is almost the same as that of bulk crystals in spite of the low concentration of CuCl in the NaCl matrix.The origin of visible photoluminescence of nanocrystalline Ge in SiO2 glassy matrix has been studied. Spectroscopic analyses of nanocrystalline Ge indicate that the room-temperature photoluminescence comes from nanocrystalline Ge of diameter of 4 nm or less. High-resolution electron microscopic studies imply that the structure of nanocrystalline Ge of diameter ≤ 4 nm differs from the diamond structure. These data suggest that new nanostructure crystalline Ge having a character of direct optical transition exhibits the visible photoluminescence.
ESR Study of Porous Silicon
Authors: Cheung W. Y. , Wong S. P. , Wilson I. H. , Kan C. F. , Hark S. K. 
Published: March 2011

ABSTRACTA detailed ESR study has been performed on porous silicon on both <100> and <111> p-type silicon substrates prepared using anodization in HF under a range of conditions and the results are correlated with the light emission properties. It is found that the ESR spectra are dependent upon the orientation of the samples. The ESR defect centers are identified to be the Pb centers or Pbo centers of the Si-SiO2 system from the g-value anisotropy maps. The variation of the spin density Ns with annealing conditions has also been studied for samples annealed either in nitrogen or oxygen ambient at 200°C for various time intervals. It is concluded that the increase or decrease of Ns are due to the generation or elimination of the Pb or Pbo centers in conjunction with the oxidation process during annealing. From PL study of these samples, it is found that there is no simple correlation between the spin density and the PL intensity. However, a blue shift in the PL peak position was observed both in samples after a post-annealing etch in HF solution, and in samples annealed in oxygen without a post-annealing etch. This blue shift supports the quantum confinement model of light emission from porous silicon.
Observation of Paramagnetic Silicon Dangling Orbitals in Luminescent Porous Silicon
Authors: Rong F. C. , Poindexter E. H. , Harvey J. F. , Morton D. C. , Lux R. A. , Gerardi G. J. 
Published: March 2011

ABSTRACTWe have detected two dominant paramagnetic centers in porous silicon by electron paramagnetic resonance (EPR). One of them is isotropic, assigned to a defect in amorphous silicon oxide in the porous silicon layer. The other is anisotropic, and is very much like a Pb center at a planar Si/SiO2 interface. This EPR center is unambiguously identified as an •Si≡Si3 moiety, a silicon with dangling orbital, back-bonded to three silicon atoms, by 29 Si hyperfine structure (HFS) associated with the dangling orbital, and 29 Si superHFS from three neighboring silicon atoms, as similarly observed in the usual planar surface Pb structure. The dangling orbitals are highly localized and heavily p character. The disposition of dangling orbitals is evidence that the skeletal structure of luminescent porous silicon is crystalline and has a lattice which is aligned and continuous with the wafer substrate. The possibility that these centers are the major photoluminescent killers or quenchers is not supported by our hydrogen annealing experiments.
High Spatial Resolution Mapping of Porous Silicon
Authors: Ettedgui E. , Peng C. , Tsybeskov L. , Gao Y. , Fauchet P. M. , Carver G. E. , Mizes H. A. 
Published: March 2011

ABSTRACTPorous silicon (PSI) samples with high photoluminescence (PL) efficiency were examined using microscopic mapping techniques including scanning election microscopy (SEM) and spatially resolved photoluminescence (SRPL). Studies of the growth conditions indicate that the homogeneity of the PL and the surface roughness of the sample depend on the preparation procedure of the PSI layer. SEM and spatially-resolved reflectance scans of an n-type sample with a PSI layer on the order of 100 μm reveal a highly fractured surface. SRPL of the same sample shows non uniform PL on a scale of 5 μm. Cross-sectional analysis of the samples with SRPL and SEM reveals the intricate multilayer structure of the PSI film. The top portion of the PSI film is largely responsible for the PL and is composed of isolated column-like structures. We have also observed cross-shaped structures reminiscent of stress fractures on the surface of PSI films using SEM or optical microscopy. Furthermore, atomic force microscopy (AFM) and SEM measurements of the surface of PSI films of intermediate thickness reveal that samples which appear smooth on ̃ lμm scale are actually covered with clumped structures on the order of 100 to 150 nm.
Porous Silicon Photoluminescence Versus HF Etching: No Correlation with Surface Hydrogen Species
Authors: Robinson M. B. , Dillon A. C. , George S. M. 
Published: March 2011

ABSTRACTThe photoluminescence and infrared absorbance of electrochemically anodized porous silicon samples were examined as a function of hydrofluoric acid (HF) etching time. Transmission FTIR spectroscopy measurements revealed that the infrared absorbance from silicon hydrogen surface species was largest for the initial porous silicon samples and immediately decreased with HF etching. In contrast, the photoluminescence did not appear until after HF etching times of 20–80 minutes, depending on initial sample porosity. Subsequently, the photoluminescence intensity increased, reached a maximum, and then progressively decreased versus HF etching time. These HF etching results demonstrate that there is no direct correlation between the photoluminescence and the silicon hydrogen surface species.
Electron Spin Resonance Investigations of Rapid Thermal Oxidized Porous Silicon
Authors: Linke H. , Omling P. , Meyer B. K. , Petrova-Koch V. , Muschik T. , Lehmann V. 
Published: March 2011

ABSTRACTWe studied the defect properties present in rapid thermal oxidized porous silicon (RTOPS) by Electron Spin Resonance (ESR). Two different types of defects are distinguished, one similar to the ones observed in damaged c-Si, and in a-Si. The second one is probably related to the Pbo center at the Si/SiO2 interface. The minimum density of 1016 cm-3 is observed for the as etched and for the 900°C oxidized samples, but reaches a maximum of 8×1018 cm-3for the 600°C samples. The PL intensity anticorrelates with the defect densities, which shows that nonradiative recombination via defects is a very powerful channel in quenching the PL efficiency.
Formation Mechanism of Microporous Silicon: Predictions and Experimental Results
Authors: Lehmann V. , Gösele U. 
Published: March 2011

ABSTRACTRecently we presented a formation mechanism for micro-porous silicon which is based on a depletion of holes in the porous region due to quantum confinement. This theory allows predictions concerning the dependence of the porous morphology on the formation conditions. It is the purpose of this work to check whether these predictions are in accordance with experimental observations.
Effect of Laser Illumination on Oxidization of Porous Silicon
Authors: Zhang L. Z. , Mao J. C. , Zhang B. R. , Zhu W. X. , He Y. L. , Song H. Z. , Duan J. Q. , Qin G. G. 
Published: March 2011

ABSTRACTWe have studied the effect of laser illumination (argon laser line of 488 nm) on the oxidization process of the inner surfaces of porous silicon (PS) by measuring the photoluminescence (PL), Fourier-transform infrared (FTIR) absorption and x-ray photoelectron spectroscope and contrasted the variations of PL and FTIR spectra of the PS treated in the following four ways: 1. In vacuum with laser illumination (LI) with power density of 12 mW / mm2. 2. In oxygen with LI. 3. In oxygen without LI. The times for all the above three treatments were 1 h. 4. Storage in air for 2 months without LI. The PL peak of PS showed serious degradation and a blue shift in case 2 but only a moderate degradation and no shift in case 1. The results of FTIR absorption show that the LI in an atmosphere of oxygen enhanced greatly the increase of oxygen-related absorption bands and the decrease of various silicon-hydrogen vibrational mode absorption bands.
Mechanism of in-Situ Photoluminescence Decay in Porous Silicon and its Application to Maskless Patterning
Authors: Takai Mikio , Indou Sanae , Murase Hisanori 
Published: March 2011

ABSTRACTPL decay in a time scale of ms for fresh porous Si surfaces was investigated for different atmospheres and excitation intensities to clarify the mechanism of the PL decay. The PL excitation intensity and atmosphere were found to affect the decay of PL, which was due to laser enhanced oxidation.Locally PL excited areas of porous Si were also found to be etched in a HF solution. Maskless patterning using this effect could be performed by a scan of a focused laser beam followed by HF etching.
Brønsted and Lewis Base Quenching of Photoemission from Luminescent ‘Porous Silicon’: Surface Protons in the Luminescence Mechanism
Authors: Chun J. K. M. , Bocarsly A. B. , Cottrellt T. R. , Benzigert J. B. , Yee J. C. 
Published: March 2011

ABSTRACTThe photoluminescence (PL) observed from porous silicon (PS) is found to be very sensitive to pH. Brønsted bases quench the PL and simultaneously produce a blue shift of the p-type PS emission. Similarly, PL of n-type PS is quenched, but the emission is red shifted. Exposure to acids enhances PL and reverses the quenching due to base exposure. A pKa of 3–4 was determined for PS formed on both n- and p-type substrates, and identifies an acidic surface proton as a primary component in the PL mechanism. Variations in the intensity and energy distribution of PL as a function of temperature suggest that: 1) small changes in the hydration state of the surface may affect the emission, and 2) at least two luminescent species exist on the surface of PS; one of which is pH and temperature sensitive. SO2, a Lewis base, also quenches the PL of p-type PS quickly and reversibly. Exposure to acid is unnecessary for restoration of the PL. In contrast to reactivity with Brønsted bases, the reversibility with SO2 argues for a different quenching mechanism. Preliminary experiments show that PL is significantly quenched, ∼2–5%, by concentrations of ∼30ppm SO2 in Ar.
Visible Photoluminescence and Microstructure of Annealed and Chemically Etched Amorphous Si
Authors: Jung K. H. , Shih S. , Kwong D. L. , Cho C. C. , Gnade B. E. 
Published: March 2011

ABSTRACTWe have studied the visible photoluminescence (PL) and microstructure of porous Si layers (PSLs) fabricated by the chemical etching of annealed amorphous Si (a-Si). The a-Si layers were partially crystallized by annealing between 550°C-1150°C in N2 and the PSL formed by etching in a HF-HNO3-based solution. No visible PL was observed after etching of unannealed a-Si. Visible PL was detected after etching a-Si layers first annealed at temperatures ≥725°C, coinciding with the observation of Si microcrystallites in the annealed layer prior to etching. The results suggest that an initial crystalline structure is important for fabricating luminescent PSLs.
Optoelectronic Characterizations of Porous Silicon
Authors: Koshida Nobuyoshi , Koyama Hideki 
Published: March 2011

ABSTRACTThe optoelectronic properties of porous Si (PS) have been investigated in relation to the visible luminescence characteristics. First, the electronic structure has been characterized by spectroscopic ellipsometry and synchrotron orbital radiation (SOR) reflection spectra analyses. A retention of the original crystallinity, accompanied by a band gap widening, is confirmed by the optical reflection spectra and the optical constants behavior. Second, it is shown that there exists an intrinsic correlation between the visible photoluminescence characteristics of PS and its interfacial and electrical properties. These experimental results suggest that in the visible luminescence mechanism of PS, both band modification in Si crystallites and passivation at their surface play a complementary role to each other. The former ensures sufficient electronic excitation and the latter contribute to suppression of nonradiative relaxation.
Photoconductivity and Carrier Transport in Porous Silicon
Authors: Heben M. J. , Tsuo Y. S. 
Published: March 2011

ABSTRACTWe present results from our investigations of the transport properties of p-type Si/porous silicon/Au devices. Current-voltage measurements were performed as a function of temperature from room temperature down to 23K and indicate that a tunneling mechanism governs the transport properties of these devices. Photocurrent spectroscopy measurements were performed as a function of temperature and excitation wavelength and support the conclusion that a tunneling mechanism is operative in these devices. The external quantum efficiencies of our porous-silicon-based structures can be greater than 20%, and the shape of the photocurrent spectra of porous-silicon-based devices, when compared to that of a p-type Si/Au diode, suggests that carriers photogenerated within porous silicon can be collected in an external circuit.
Mechanism of Electron Injection During the Anodic Oxidation of Silicon
Authors: Chazalvel J.-N. , Ozanam F. 
Published: March 2011

ABSTRACTn-Si photoanodes have been found to exhibit photocurrent multiplication during the first seconds of exposure to a fluoride-free, acidic electrolyte. This shows that, in contrast with earlier hypotheses, photocurrent doubling is not directly related to the presence of fluoride in the electrolyte, but rather must arise from an electron injection mechanism associated with the Si-H bonds initially present at the Si surface. It also suggests that the electroluminescence which has been observed during the anodic oxidation of porous silicon most probably stems from the same electron-injection mechanism.