Effects Of Rapid Thermal Processing Research Articles

CH3NH3PbI3/CdS planar photovoltaic junction by spin-dip coating: Studies on the effects of PbI2 layer thickness and rapid thermal treatments

Photovoltaic structures of Glass/FTO/CdS/CH3NH3PbI3 have been fabricated and the effects of rapid thermal processing (RTP) on these structures are investigated. First, CdS thin films were deposited by chemical bath deposition on which PbI2 by spin coating followed by 60 min dipping in 0.1 M CH3NH3I solution, varying PbI2 concentrations (0.6–1 M). Studies on the effects of RTP of the CH3NH3PbI3 films and the PbI2 precursor layers revealed an increase in the open-circuit voltage as well as the short curcuit current due to the improved crystallinity and the change in the preferential orientation of the perovskite growth leading to better charge transport. The samples were characterized by X-ray diffractometry, X-ray photoelectron spectroscopy, and scanning electron microscopy. The optical and electrical properties were also measured.The perovskite films formed exhibited tetragonal crystalline structure with uniform and compact morphology. The thin films were photoconductive and possessed a direct band gap of 1.5–1.6 eV. The XPS analysis showed the presence of the constituent elements and their chemical states. The photovoltaic parameters of the best cells were: Voc = 0.62 V, Jsc = 5.2 mA/cm2, FF = 0.43 and an efficiency of 1.2%. The present work span the scope of the hybrid perovskite mateirals in the conventional p-n heterojuntion solar cells free of any organic HTM layers.

Effects of rapid thermal processing on chemically deposited antimony sulfide thin films

In this paper, we report studies on rapid thermal processed (RTP) antimony sulfide (Sb2S3) thin films grown on glass and Mo-coated glass substrates by chemical bath deposition. Structure, morphology, elemental composition, optical and electrical properties of the thin films processed at different temperatures (325–700 °C) for 1–5 min were evaluated. X-ray diffractometry and Raman spectral studies showed the crystalline nature of the thin films. XPS analysis demonstrated the elemental composition and chemical states. Optical band gap of the films was evaluated from the optical absorption spectra, and the bandgap values were in the range of 1.7–2.1 eV. All the RTP samples showed photocurrent response. Crystallinity and morphology of the films were modified by varying RTP temperature and time.

Effect of Rapid Thermal Processing on Light-Induced Degradation of Carrier Lifetime in Czochralski p-Type Silicon Bare Wafers

The electrical properties of Czochralski silicon (Cz-Si) p-type boron-doped bare wafers have been investigated after rapid thermal processing (RTP) with different peak temperatures. Treated wafers were exposed to light for various illumination times, and the effective carrier lifetime (τ eff) measured using the quasi-steady-state photoconductance (QSSPC) technique. τ eff values dropped after prolonged illumination exposure due to light-induced degradation (LID) related to electrical activation of boron–oxygen (BO) complexes, except in the sample treated with peak temperature of 785°C, for which the τ eff degradation was less pronounced. Also, a reduction was observed when using the 830°C peak temperature, an effect that was enhanced by alteration of the wafer morphology (roughness). Furthermore, the electrical resistivity presented good stability under light exposure as a function of temperature compared with reference wafers. Additionally, the optical absorption edge shifted to higher wavelength, leading to increased free-carrier absorption by treated wafers. Moreover, a theoretical model is used to understand the lifetime degradation and regeneration behavior as a function of illumination time. We conclude that RTP plays an important role in carrier lifetime regeneration for Cz-Si wafers via modification of optoelectronic and structural properties. The balance between an optimized RTP cycle and the rest of the solar cell elaboration process can overcome the negative effect of LID and contribute to achievement of higher solar cell efficiency and module performance.

Effect of Rapid Thermal Process on the Recrystallization and Precipitation in Non-Oriented Electrical Steels Produced by Twin-Roll Strip Casting

A Fe-1.3% Si non-oriented silicon steel strip was produced by twin-roll strip casting process, and subsequently treated with cold rolling and annealing. The effect of heating rates on the recrystallization and precipitation behavior of second phase particles (AlN and MnS) was investigated by MMS-200 thermal mechanical simulator. It was found that the recrystallization area fraction decreased obviously with the increase of heating rate. At the heating rate of 5 °C/s, the recrystallization rate gradually decreased with the extension of holding time, but it increased at the rapid heating rates. The particle’s sizes mainly concentrated in 50~200 nm at the heating rate of 5 °C/s during annealing. The number of particles under 50nm increased gradually and the number of precipitates between 50~400 nm reduced significantly when the heating rate was increased to 50~300 °C/s. The results indicated that the rapid heating rate could refine the size of precipitates and decrease the number of particles above 50nm.

AgSb(SxSe1‐x)2 thin films by rapid thermal processing of Sb2S3‐Ag‐Se thin films for photovoltaic applications

AbstractSilver antimony sulfoselenide thin films have been investigated for photovoltaic applications. In the present work, we report preparation of AgSb(SxSe1‐x)2 by a rapid thermal processing of pre‐annealed Sb2S3/Ag/Se/Ag/Se layered structures. Sb2S3thin films were deposited by chemical bath deposition and Ag by thermal evaporation. Silver (Sb2S3/Ag) layered precursors were dipped in Na2SeSO3 solution followed by annealing and then rapid thermal processing. Also, photovoltaic structures were prepared using AgSb(SxSe1‐x)2 thin films as absorber and CdS as window material. The effects of rapid thermal processing on the structure, morphology and properties of these thin films were studied. Characterization of the absorber materials was done using X‐ray diffraction, X‐ray photoelectron spectroscopy, Atomic force microscopy, Optical absorption spectroscopy and Current‐voltage characteristics. Analysis of J ‐V characteristics of the photovoltaic structures under AM1.5 illumination before and after rapid thermal treatment showed Voc in a range of 457 to 473 mV and Jsc of 5.8 to 7.2 mA/cm2. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of rapid thermal processing on copper precipitation in p/p+ silicon epitaxial wafers with heavily boron-doped substrates

The effect of rapid thermal processing (RTP) on the formation of copper precipitation in p/p+ silicon (Si) epitaxial wafers was systematically investigated by defect etching and optical microscopy. After RTP preannealing at high temperature (1250 °C/60 s, with cooling rate 30 K/s) followed by the 750 °C/8 h + 1050 °C/16 h low-high (L-H) two-step annealing, it was revealed that the bulk microdefects were found only inside the p+ substrate, manifesting no defects generated in the epitaxial layer. However, it was found that the width of denude zone (DZ) in samples only subjected to L-H two-step annealing was narrower than that of epitaxial layer, which meant that oxygen precipitation was formed in epitaxial layer. It can be concluded that RTP was beneficial to the formation of DZ. Additionally, it was found that the width of DZ has a sharp dependence on the introducing temperature of copper contamination, that is, the corresponding equilibrium concentration of interstitial copper in the Si influence the thermodynamics and kinetics process of the formation of copper precipitation significantly.

Effects of Rapid Thermal Process on the Microstructural, Electrical and Optical Properties of AZO Thin Films

In this paper, Al-doped ZnO thin films were deposited on glass substrates by RF magnetron sputtering and subsequently rapid thermal processing was executed under temperature range from 300°C to 600°C in order to investigate the microstructure, electrical, and optical properties of AZO films. XRD and AFM microscopy results showed that all the samples were of poly-crystalline and the grain size became larger with the increasing processing temperature. Compared with the sample as-deposited, it was shown that resistivity decreased from 1.9×10-2 to 1.48×10-3Ωcm and carrier concentration increased from 1.48×1020 to 5.59×1020 cm3 when the sample was processed at 600°C in pure nitrogen for 1 min. The highest transmittance of the samples processed at 500°C improves to 90.35% compared with the as-deposited films (68.2% ) as the wavelength varied between 400 and 900 nm.

Impact of rapid thermal processing on oxygen precipitation in heavily arsenic and antimony doped Czochralski silicon

A comparative investigation is performed on the effects of vacancies induced by rapid thermal processing on oxygen precipitation behavior in heavily arsenic- and antimony-doped Czochralski silicon wafers. It is experimentally found that vacancy-assisted oxide precipitate nucleation occurs at 800, 900, and 1000 °C in the Sb-doped wafers, while it only occurs at 800 °C in the As-doped ones. Density functional theory calculations indicate that it is energetically favorable to form AsVO and SbVO complexes in As- and Sb-doped silicon crystals, respectively. These complexes might act as precursors for oxide precipitate nucleation under appropriate conditions. The difference between the effects of rapid thermal processing -induced vacancies on oxide precipitate nucleation in the heavily As- and Sb-doped Cz silicon crystals is tentatively elucidated based on density functional theory calculations revealing the difference in binding energies of AsVO and SbVO complexes.

Effect of Rapid Thermal Processing on the structural and device properties of (Ag,Cu)(In,Ga)Se2 thin film solar cells

(AgwCu1−w)(In1−xGax)Se2 alloy absorber layers with w≈0.8 and x≈0.78 ratios were deposited using multi-source elemental evaporation and analyzed by glancing incidence X-ray diffraction, scanning electron microscopy combined with energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The effect of Rapid Thermal Processing (RTP) on the structure and composition of the near-surface layers was investigated. It was found that the RTP doesn't have a noticeable effect on the grain size and roughness of the film surface. On the other hand, additional reflections of the films with 0.5≤Ga/(Ga+In)<1 and Ag/(Ag+Cu)>0.5, due to an ordered defect phase which is confined to the near-surface region of the film, are completely diminished after RTP with excess Se present. X-ray photoelectron spectroscopy results show that RTP with excess Se present altered the distribution of elements, rendering the film surface less group I deficient after that process. Consequently, atomic ratios were changed from the composition of I1III5VI8 compound to the composition close to that of I1III3VI5 ordered defect phase. Additionally, the RTP treatment, especially with excess Se, significantly enhanced solar cell efficiency performance due to an improvement in the open circuit voltage.

Effects of rapid thermal process on the junction properties of aluminum rear emitter solar cells

N-type silicon with aluminum emitters for rear junctions was studied; aluminum back surface fields were replaced with n-type silicon wafers. Aluminum rear emitters for n-type silicon solar cells were studied with various rapid thermal processing conditions. With fast ramping-up and fast cooling, an aluminum rear junction was formed uniformly with low emitter recombination current. The effects of junction quality on solar cell efficiency were investigated.

Effects of High Temperature Rapid Thermal Processing on the Formation of Oxidation Induced Stacking Faults in 300 mm Nitrogen-Doped Czochralski Silicon Wafers

Oxidation induced stacking faults (OSFs) are more readily generated in nitrogen-doped Czochralski (NCz) silicon wafers because of possessing more grown-in oxygen precipitates (OPs). This issue is worthy to be addressed. In this work, the effects of rapid thermal processing (RTP) at high temperature in different atmospheres on the formation of OSFs in 300 mm NCz silicon wafers have been investigated. It is found that the prior RTP at 1250 °C in Ar atmosphere can effectively annihilate OSFs, while that in N2 atmosphere promotes the formation of OSFs instead. The reason for this result has been elucidated in the text.

Effect of the annealing treatments on the electroluminescence efficiency of SiO2 layers doped with Si and Er

We studied the effect of rapid thermal processing and furnace annealing on the transport properties and electroluminescence (EL) of SiO2 layers doped with Si and Er ions. The results show that for the same annealing temperature, furnace annealing decreases the electrical conductivity and increases the probability of impact excitation, which leads to an improved external quantum efficiency. Correlations between predictions from phenomenological transport models, annealing regimes and erbium EL are observed and discussed.

Optical properties and chemical bonding characteristics of amorphous SiNX:H thin films grown by the plasma enhanced chemical vapor deposition method

Amorphous silicon nitride (SiNX:H) thin films grown by the plasma enhanced chemical vapor deposition (PECVD) method are presently the most important antireflection coatings for crystalline silicon solar cells. In this work, we investigated the optical properties and chemical bonding characteristics of the amorphous SiNX:H thin films deposited by PECVD. Silane (SiH4) and ammonia (NH3) were used as the reactive precursors. The dependence of the growth rate and refractive index of the SiNX:H thin films on the SiH4/NH3 gas flow ratio was studied. The chemical bonding characteristics and the surface morphologies of the SiNX:H thin films were studied using the Fourier transform infrared spectroscopy and atomic force microscopy, respectively. We also investigated the effect of rapid thermal processing on the optical properties and surface morphologies of the SiNX:H thin films. It was found that the rapid thermal processing resulted in a decrease in the thickness, increase in the refractive index, and coarser surfaces for the SiNX:H thin films.

Induced changes on visible emission and conductive type in N-doped ZnO films by rapid thermal process

The erratic p-type conductivity in nitrogen-doped ZnO film is still under investigation and has been debated up to now. In this study, the authors have studied the effect of rapid thermal process (RTP) on the properties of N-doped ZnO films grown by metal-organic chemical vapor deposition. Hall-effect measurements show that the sample is of p-type as the RTP temperature is lower than 350 °C while, as the RTP temperature increased up to 550 °C or higher, the conduction-type of the sample changed to be n-type. Correspondingly, obvious D and G peaks, which are related to graphite clusters, are observed to increase their intensity with RTP temperature, indicating that interstitial or substitutional carbon atoms may migrate to form carbon clusters in the grain boundary during RTP. RTP is also found to lead to significant changes on the photoluminescence of the samples, with enhanced visible emissions observed as RTP temperature increased. Similar changes are observed on the intensity ratios of the D over G peaks and the visible emission around 600 nm over the near-band-edge emission. This indicates that besides zinc vacancy (VZn) and oxygen vacancy (VO), which are popularly ascribed as the origins of the visible emissions around 500 and 550 nm, carbon clusters may be a possible origin of the visible emission around 600 nm. Finally, carbon clusters formed in the grain boundary are also supposed to at least partly be responsible for the type transition caused by RTP.

Effects of Rapid Thermal Processing on Microstructure and Optical Properties of As-Deposited Ag2O Films by Direct-Current Reactive Magnetron Sputtering

(111) preferentially oriented Ag2O film deposited by direct current reactive magnetron sputtering is annealed by rapid thermal processing at different annealing temperatures for 5 min. The film microstructure and optical properties are then characterized by x-ray diffractometry, scanning electron microscopy, and spectrophotometry, respectively. The results indicate that no clear Ag diffraction peak is discernable in the Ag2O film annealed below 200°C. In comparison, the Ag2O film annealed at 200°C begins to exhibit characteristic Ag diffraction peaks, and in particular the Ag2O film annealed at 250°C can demonstrate enhanced Ag diffraction peaks. This implies that the threshold of the thermal decomposition reaction to produce Ag particles is approximately 200°C for the Ag2O film. In addition, an evolution of the film surface morphology from compact and pyramid-like to a rough and porous structure clearly occurred with increasing annealing temperature. The porous structure might be attributable to the escape of the oxygen produced during annealing, while the rough surface might originate from the reconstruction of the surface. The dispersion of interference peak intensity in the reflectance and transmission spectra could be attributed to the Ag particles produced. The lowered crystallinity and Ag particles produced induce a lattice defect, which results in an enhanced transmissivity in the violet region and a weakened transmissivity in the infrared region.

Effect of Oxygen Precipitates in Annealed Electron Irradiated Czochralski Silicon

The precipitation of oxygen has been investigated for 1.5 MeV electron irradiated silicon samples with the dose of 3.5×1017 e/cm2. It has found that electron irradiation accelerated the oxygen precipitation in CZ-Si under higher annealing temperature. In addition, the effect of rapid thermal process (RTP) on the oxygen precipitation and on the denuded zone (DZ) formation in electron irradiated silicon wafers have been investigated by using optical microscope methods. The DZ can be formed at the surface in electron irradiated silicon wafers subjected to RTP pre-annealing. Furthermore, the width of DZ decreases with the RTP temperature.

Rapid-thermal-processing-based internal gettering for heavily boron-doped Czochralski silicon

The effect of rapid-thermal processing (RTP) ambients on the formation of oxygen precipitates and denuded zone (DZ) in heavily boron-doped (HB) Czochralski (Cz) silicon by a low-high (L-H) two-step annealing (800°C∕4h+1000°C∕16h) has been investigated. It was found that after the L-H two-step annealing, there was a high density of bulk microdefects (BMDs) and no observable DZ was formed near the surface in HB Cz silicon wafers preannealed by the RTP in Ar ambient, while the BMD density was quite low in HB Cz silicon wafers preannealed by the RTP in O2 ambient. However, applying the preannealing of RTP sequentially in Ar and O2 ambients allowed us to obtain a high density of BMDs in combination with a sufficient DZ by the subsequent L-H two-step annealing. This approach offers a pathway to optimize internal gettering for HB Cz silicon.

Effects of rapid thermal processing on oxide precipitation in conventional and nitrogen‐doped Czochralski silicon

AbstractIn this paper, the effects of vacancies introduced by rapid thermal processing (RTP) on nucleation and growth of oxide precipitates in Czochralski (Cz) silicon are elucidated. Moreover, the nitrogen and vacancy enhancement roles in oxide precipitation are differentiated through designing specific annealing schemes. Furthermore, it is pointed out that the RTP‐based internal gettering process for a nitrogen‐doped Cz silicon wafer should be different from that for a conventional Cz silicon wafer in order to strengthen the intrinsic gettering capability. (© 2006 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Rapid-thermal-processing-based intrinsic gettering for nitrogen-doped Czochralski silicon

In order to optimize the intrinsic gettering (IG) process based on the rapid thermal processing (RTP) for nitrogen-doped Czochralski (NCZ) silicon wafer, the effects of RTP and the following nucleation anneal on oxygen precipitation in NCZ silicon and conventional CZ silicon wafers have been comparatively investigated. It was found that, for NCZ silicon, the RTP at enough high temperature (e.g., 1250°C) was necessary for generation of high density of bulk microdefects (BMDs) in the subsequent anneals despite the nitrogen enhancement effect on oxygen precipitation. With enough high concentration of vacancies introduced by the RTP at 1250°C, for the conventional CZ silicon wafer, the vacancy enhancement effect on the nucleation of oxygen precipitates was most significant at 800°C; while for NCZ silicon wafer, the vacancies and nitrogen atoms coacted most remarkably to nucleate the oxygen precipitates during the ramping anneal from 800to1000°C. It was further found that the doped nitrogen is superior to the vacancy to enhance the nucleation of oxygen precipitates at temperatures of 900–1000°C. Moreover, in order to maximize the density of BMDs, the RTP-based IG process for NCZ silicon wafer should be different from that for the conventional CZ silicon wafer.

Effect of rapid thermal processing on high temperature oxygen precipitation behaviour inCzochralski silicon wafer

The effect of rapid thermal processing (RTP) on the oxygen precipitation occurring at1050 °C in a Czochralski (CZ) silicon wafer has been investigated. It has been proved thatthe RTP-induced vacancies only enhance the early stage oxygen precipitation at1050 °C in terms of the precipitation rate. Furthermore, it is somewhat unexpected that after a lengthy1050 °C anneal the oxygen precipitates generated in the CZ silicon wafer with prior RTP treatmenthad considerably lower density and larger sizes in comparison with those generated in theCZ silicon wafer without prior RTP treatment. The reason for this is that the prior RTPtreatment will dissolve some of the grown-in oxygen precipitates, thus making the RTP-treatedwafer possess fewer nuclei contributing to oxygen precipitation in the subsequent1050 °C anneal. Moreover, the numbers of resulting precipitated oxygen atoms due to a lengthy1050 °C anneal were nearly the same in the CZ silicon wafers with and without prior RTPtreatment. Additionally, it has been illustrated that the high temperature RTP hassuperior capability to dissolve the existing oxygen precipitates. It is worthwhile to point outthat, when addressing the effect of RTP on the oxygen precipitation behaviour duringthe subsequent anneal, two functions arising from the RTP treatment, that is,the injection of vacancies into the silicon wafer and the dissolution of grown-inoxygen precipitates existing in the silicon wafer, should be taken into account.