TRANSIENT SCANNING ELECTRON BEAM ANNEALING METHODS USED TO STUDY DIFFUSION AND DEFECTS IN IMPLANTED SILICON.

Rapid thermal annealing of arsenic and boron difluoride implants, such as those used for source/drain regions in CMOS, has been carried out using a scanning electron beam annealer, as part of a study of transient diffusion effects. Three types of e-beam anneal have been performed, with peak temperatures in the range 900 -1200 degree C; the normal isothermal e-beam anneals, together with sub-second fast anneals and 'dual-pulse' anneals, in which the sample undergoes an isothermal pre-anneal followed by rapid heating to the required anneal temperature is less than 0. 5s. The diffusion occuring during these anneal cycles has been modelled using SPS-1D, an implant and diffusion modelling program developed by one of the authors. This has been modified to incorporate simulated temperature vs. time cycles for the anneals. Results are presented applying the usual equilibrium clustering model, a transient point-defect enhancement to the diffusivity proposed recently by Fair and a new dynamic clustering model for arsenic. Good agreement with SIMS measurements is obtained using the dynamic clustering model, without recourse to a transient defect model.

Optical investigations of the effect of solvent and thermal annealing on the optoelectronic properties of Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) films

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is one of the most promising conducting polymers that can be used as transparent electrode or as buffer layer for organic electronic devices. However, when used as an electrode, its conductivity has to be optimized either by the addition of solvents or by post-deposition processing. In this work, we investigate the effect of the addition of the polar solvent dimethylsulfoxide (DMSO) to an aqueous PEDOT:PSS solution on its optical and electrical properties by the implementation of the Drude model for the analysis of the measured pseudo-dielectric function by Spectroscopic Ellipsometry from the near infrared to the visible-far ultraviolet spectral range. The results show that the addition of DMSO increases significantly the film conductivity, which reaches a maximum value at an optimum DMSO concentration as it has confirmed by experimentally measured conductivity values. The post-deposition thermal annealing has been found to have a smaller effect on the film conductivity. © 2013 Elsevier B.V.

Evolution of vertical phase separation in P3HT:PCBM thin films induced by thermal annealing

The achievement of the desirable morphology at the nanometer scale of bulk heterojunctions consisting of a conjugated polymer with fullerene derivatives is a prerequisite in order to optimize the power conversion efficiency of organic solar cells. The various experimental conditions such as the choice of solvent, drying rates and annealing have been found to significantly affect the blend morphology and the final performance of the photovoltaic device. In this work, we focus on the effects of post deposition thermal annealing at 140 °C on the blend morphology, the optical and structural properties of bulk heterojunctions that consist of poly(3-hexylthiophene) (P3HT) and a methanofullerene derivative (PCBM). The post thermal annealing modifies the distribution of the P3HT and the PCBM inside the blend films, as it has been found by Spectroscopic Ellipsometry studies in the visible to far-ultraviolet spectral range. Phase separation was identified by AFM and GIXRD as a result of a slow drying process which took place after the spin coating process. The increase of the annealing time resulted to a significant increase of the P3HT crystallinity at the top regions of the blend films. © 2011 Elsevier B.V. All rights reserved.

Thermal annealing effect on the nanomechanical properties and structure of P3HT:PCBM thin films

Nanostructured polymer-fullerene thin films are among the most prominent materials for application in high efficient polymer solar cells. Specifically, poly(3-hexylthiophene) (P3HT) and fullerene derivatives (PCBM) blends are used as the donor/acceptor materials forming a bulk heterojunction. Although P3HT:PCBM properties have been extensively studied, less light has been set on its nanomechanical properties, which affect the device service life. In this work Atomic Force Acoustic Microscopy (AFAM), Atomic Force Spectroscopy and Nanoindentation were used to study the effect of the fullerene presence and the annealing on the P3HT:PCBM nanomechanical behavior. The P3HT:PCBM thin films were prepared by spin coating on glass substrates and then annealed at 100 °C and 145 °C for 30 min. Large phase separation was identified by optical and Atomic Force Microscopy (AFM) for the annealed samples. Needle-like PCBM crystals were formed and an increase of the polymer crystallinity degree with the increase of the annealing temperature was confirmed by X-ray diffraction. AFAM characterization revealed the presence of aggregates close to stiff PCBM crystals, possibly consisting of amorphous P3HT material. AFM force-distance curves showed a continuous change in stiffness in the vicinity of the PCBM crystals, due to the PCBM depletion near its crystals, and the AFM indentation provided qualitative results about the changes in P3HT nanomechanical response after annealing. © 2011 Elsevier B.V. All rights reserved.

Nonradiative recombination centers in Ga(As,N) and their annealing behavior studied by Raman spectroscopy

Nitrogen-related defects in diluted Ga(As,N) have been detected by Raman scattering in resonance with the localized E+ transition. These defects are attributed to local vibrational modes of nitrogen dimers on Ga- and As-lattice sites. Rapid thermal annealing under appropriate conditions is found to be able to remove the nitrogen dimers. The required minimum annealing temperature coincides with the threshold-like onset of strong, near-band-gap photoluminescence. This finding suggests that the nitrogen dimers are connected with nonradiative recombination centers. (C) 2004 American Institute of Physics.

Growth and annealing study of Mg-doped AlGaN and GaN/AlGaN superlattices

Mg-doped AlGaN and GaN/AlGaN superlattice are grown by metalorganic chemical vapour deposition (MOCVD). Rapid thermal annealing (RTA) treatments are carried out on the samples. Hall and high resolution x-ray diffraction measurements are used to characterize the electrical and structural prosperities of the as-grown and annealed samples, respectively. The results of hall measurements show that after annealing, the Mg-doped AlGaN sample can not obtain the distinct hole concentration and can acquire a resistivity of 1.4 x 10(3) Omega cm. However, with the same annealing treatment, the GaN/AlGaN superlattice sample has a hole concentration of 1.7 x 10(17) cm(-3) and of Mg acceptors, which leads to higher hole concentration and lower p-type resistivity.

Post-growth and in situ annealing on GaInNAs(Sb) and their application in 1.55 mu m lasers

Rapid thermal annealing (RTA) has been demonstrated as an important way to improve the crystal quality of GaInNAs(Sb)/GaAs quantum wells. However little investigation has been made into their application in laser growth, especially at a wavelength of 1.55 mu m. When a GaAs-based laser is grown, AlGaAs is usually used for cladding layers. The growth of the p-cladding layer usually takes 30-45 min at a growth temperature higher than that of the GaInNAs(Sb) active region, which affects the material quality. To investigate this effect, various post-growth annealing processes were performed to simulate this process. Great enhancement of the PL intensity was obtained by a two-step process which consisted of annealing first at 700 degrees C for 60 s and then at 600 degrees C for 45 min. We transferred this post-growth annealing to in situ annealing. Finally, a GaInNAsSb laser was grown with a 700 degrees C in situ annealing process. Continuous operation at room temperature of a GaAs-based dilute nitride laser with a wavelength beyond 1.55 mu m was realized for the first time.

Electrical properties of B-doped polycrystalline silicon thin films prepared by rapid thermal chemical vapour deposition

In this paper, about 30 mu m thick B-doped polycrystalline silicon (poly-Si) thin films were deposited on quartz substrates, n-type single crystalline silicon wafers and p(++)-type poly-Si ribbons by a rapid thermal chemical vapour deposition system in a temperature range from 1000 to 1150 degrees C. Activation energy measurement and room temperature/temperature dependent Hall effect measurement were performed on the poly-Si thin films prepared on the former two kinds of substrates, respectively. It seems that the electrical properties of as-prepared poly-Si thin films could be qualitatively explained by Seto's grain boundary (GB) trapping theory although there is a big difference between our samples and Seto's in gain size and film thickness etc. The experimental results reconfirm that GB itself is a kind of most effective recombination center with trapping level near the midgap and trapping state density in the order of 1012 cm(-2) magnitude. Electron beam induced current measurements on the poly-Si thin films prepared on the poly-Si ribbons also show that severe recombination occurs at the positions of GBs. (c) 2005 Elsevier B.V All rights reserved.

Annealing and activation of silicon implanted in semi-insulating InP substrates

We have investigated the annealing and activation of silicon implanted in both as-grown Fe-doped semi-insulating (SI) InP substrate and undoped SI InP substrate obtained by annealing high purity conductive InP wafer (wafer-annealed). Si implantations were performed at an energy of 500 keV and a dose of 1 X 10(15) cm(-2). Following the implantations, rapid thermal annealing (RTA) cycles were carried out for 30 s at different temperatures. The results of Raman measurements show that for 700degreesC/30s RTA, the two Si-implanted SI InP substrates have acquired a high degree of lattice recovery and electrical activation. However, further Hall measurements indicate that the carrier concentration of the wafer-annealed SI InP substrate is about three times higher than that of the as-grown Fe-doped SI InP substrate. The difference can be ascribed to the low Fe concentration of the wafer-annealed SI InP substrate.These experimental data imply that the use of the wafer-annealed SI InP substrate can be conducive to the improvement of InP-based device performances. (C) 2003 Elsevier Ltd. All rights reserved.

Thermal annealing behaviour of Pt on n-GaN Schottky contacts

The structural evolution and temperature dependence of the Schottky barrier heights of Pt contacts on n-GaN epilayer at various annealing temperatures were investigated extensively by Rutherford backscattering spectrometry, x-ray diffraction measurements, Auger electron spectroscopy, scanning electron microscopy and current-voltage measurements. The temperature dependence of the Schottky barrier heights may be attributed to changes of surface morphology of Pt films on the surface and variation of nonstoichiometric defects at the interface vicinity. Experimental results indicated the degradation of Pt contacts on n-GaN above 600 degreesC.

Thermal annealing behaviour of Ni/Au on n-GaN Schottky contacts

The Schottky behaviour of Ni/Au contact on n-GaN was investigated under various annealing conditions by current-voltage (I-V) measurements. A non-linear fitting method was used to extract the contact parameters from the I-V characteristic curves. Experimental results indicate that high quality Schottky contact with a barrier height and ideality factor of 0.86 +/- 0.02 eV and 1.19 +/- 0.02 eV, respectively, can be obtained under 5 min annealing at 600degreesC in N-2 ambience.

Influence of strain on annealing effects of In(Ga)As quantum dots

Post-growth rapid thermal annealing has been performed with In(Ga)As quantum dots (QDs) at different strain statuses. It is confirmed that the strain-enhanced interdiffusion decreases the inhomogeneous size distribution. The preferential lateral interdiffusion of QDs during annealing was observed. we attribute it to the naturally anisotropic strain distribution in/around the dots and the saturation of strain difference between the base boundary and the top of the dots. There exist strain-enhanced mechanism and vacancy diffusion enhanced mechanism during the annealing. As to which one dominates the QD interdiffusion depends on the thickness of capping layer and the annealing temperature. (C) 2002 Elsevier Science B.V. All rights reserved.

Structural properties of polycrystalline silicon films formed by pulsed rapid thermal processing

A novel pulsed rapid thermal processing (PRTP) method has been used for realizing solid-phese crystallization of amorphous silicon films prepared by plasma-enhanced chemical vapour deposit ion. The microstructure and surface morphology of the crystallized films were investigated using x-ray diffraction and atomic Force microscopy. The results indicate that PRTP is a suitable post-crystallization technique for fabricating large-area polycrystalline silicon films with good structural quality, such as large grain size, small lattice microstrain and smooth surface morphology on low-cost glass substrates.

Annealing effect on the surface morphology and photoluminescence of InGaAs/GaAs quantum dots grown by molecular beam epitaxy

Postgrowth rapid thermal annealing was performed on InGaAs/GaAs quantum dots grown by molecular beam epitaxy. The blue shift of the emission peak and the narrowing of the luminescence line width are observed at lower annealing temperature. However, when the annealing temperature is increased to 850 degrees C, the emission line width becomes larger. The TEM image of this sample shows that the surface becomes rough, and some large clusters are formed, which is due to the interdiffusion of In, Ga atoms at the InGaAs/GaAs interface and to the strain relaxation. The material is found to degrade dramatically when the annealing temperature is further increased to 900 degrees C, while emission from quantum dots can still be detected, along with the appearance of the emission from excited state. (C) 2000 Elsevier Science B.V. All rights reserved.

Effect of thermal annealing on hole trap levels in Mg-doped GaN grown by metalorganic vapor phase epitaxy

Deep trap levels in a Mg-doped GaN grown by metalorganic vapor phase epitaxy are studied with deep level transient spectroscopy (DLTS). The Mg concentration of the sample was 4.8 x 10(19) cm(-3), but the hole concentration was as low as 1.3x10(17) cm-3 at room temperature. The DLTS spectrum has a dominant peak D-1 with an activation energy of 0.41+/-0.05 eV, accompanied by two additional peaks with activation energies of 0.49+/-0.09 eV (D-2) and 0.59+/-0.05 eV (D-3). It was found that the dominant peak D-1 consists of five peaks, each of which has different activation energy and capture cross section. In order to investigate these deep levels further, we performed heat treatment on the same samples to observe the variations of activation energy, capture cross section, and amplitude of DLTS signals. It was found that the longer the heat treatment duration is, the lower the amplitude of DLTS peaks become. This suggests that the decrease of the DLTS signal originates from hydrogen atom outgoing from the film during the annealing process. The possible originality of multiple trap levels was discussed in terms of the Mg-N-H complex. (C) 2000 American Vacuum Society. [S0734-2101(00)01701-2].