Rapid Thermal Annealing Furnace Research Articles

The Mechanism Behind the Annealing‐Induced Reduction of Infrared Absorption in Zinc‐Hyperdoped Silicon

Pulsed laser hyperdoping is widely investigated as an effective method for expanding the infrared absorption of silicon. Prior to further device fabrication, thermal treatment is commonly applied to hyperdoped silicon to repair lattice defects and activate dopants. However, it is observed that thermal treatment adversely affects the infrared absorption of hyperdoped silicon, and the underlying mechanisms remain incompletely understood. Herein, zinc‐hyperdoped silicon (Si:Zn) is prepared using vacuum magnetron sputtering combined with femtosecond laser pulses, and the mechanisms of the reduction in infrared absorption during conventional annealing of Si:Zn samples are investigated. The diffusion of zinc and its precipitation as zinc clusters in silicon are observed during the annealing process, leading to a decrease in the concentration of zinc dopants within the silicon lattice and consequent attenuation of infrared absorption. Building upon this understanding, the approach of short timescale annealing subjected to infrared rapid thermal annealing furnace is proposed to be employed as a method to mitigate the adverse effects of zinc transitional precipitation, resulting in enhancement of the performance of Si:Zn optoelectronic devices.

Effect of annealing ambient on SiGe layer formation using Al–Ge paste for III–V solar cell application

A mixed paste of aluminum (Al) and germanium (Ge) (7:3) was prepared and screen-printed on silicon (Si) substrates, followed by annealing at a peak temperature of 1000 °C in an IR rapid thermal annealing furnace to investigate the liquid-phase growth of silicon–germanium (SiGe) epitaxial layers. The gas ambient during annealing was changed to investigate the effect on SiGe layer quality and physical properties. The SiGe formed samples were observed by scanning electron microscopy and energy dispersive X-ray spectroscopy. Oxygen-containing atmosphere suppressed the SiGe layer formation by oxidizing the Al particle surface, limiting the reaction of the particle to the Si surface. On the other hand, annealing in an argon atmosphere without oxygen resulted in the formation of SiGe layers with a thickness of over 30 μm.

Optical studies of pure and (Cu, Co) doped nickel zinc ferrite films deposited on quartz substrate

In this work, the optical properties of pure and doped films were investigated as a function of annealing temperature. Films with compositions Ni0.5Zn0.5Fe2O4, Ni0.35Cu0.2Zn0.45Fe2O4, and Ni0.35Co0.2Zn0.45Fe2O4 were deposited on quartz substrate using the sol–gel method. The grown films were annealed at 500 and 800 °C in a rapid thermal annealing furnace. The single-phase spinel structure of these films was confirmed by x-ray diffraction (XRD) results. The average crystallite size calculated from the XRD data was observed to increase with the annealing temperature and decrease for films doped with Cu and Co. The lattice constant was observed to decrease with the annealing temperature and increase for films doped with Cu and Co. The cross-sectional images obtained from field emission scanning electron microscope were used to calculate the thickness of these films. Ultraviolet-visible spectroscopy was used to obtain the absorbance spectra as a function of wavelength in the range of 200–800 nm. The bandgap obtained from the absorbance spectra was seen to decrease for films annealed at higher temperatures for pure and doped films. Furthermore, the bandgap of doped films was seen to decrease in comparison to that of pure films. Optical parameters such as refractive index, extinction coefficient, optical conductivity, and real and imaginary parts of the dielectric constant were observed to increase with the reduction in the bandgap.

Laser assisted processing of nanocrystalline (Ho0.05Y0.95) 2Ti2O7 films for infrared photonics

The existence of new highly thermally and chemically stable active optical materials is a challenging task for current photonics research targeted on high-power lasers. Holmium-doped titanates crystallizing in the pyrochlore lattice, represent a promising class of materials. However, their high processing temperature limits their applications in integrated optical devices. This weakness can be overcome by laser assisted processing as an alternative to common heat-treatment. The amorphous thin films were prepared by a sol-gel method followed by a dip-coating process and densified in a rapid thermal annealing furnace. The densified films were annealed by a CO2 laser beam. The laser irradiation induced a crystallization process resulting in the formation of nanocrystalline (Ho0.05Y0.95)Ti2O7. The prepared film of a thickness 576 nm exhibited an optical transmission of 91.66% close to the maximum theoretical limit of a silica substrate. The film’s refractive index at 632 nm was 2.219. The formation of the nanocrystals caused the activation of the electronic transition 5I7→5I8 at 2 μm and the emission bands showed the distinct Starks splitting which is characteristic for (Ho0.05Y0.95)Ti2O7 phosphors. The presented approach can be used to prepare transparent luminescence films with tailored optical properties by CO2 laser treatment and together with direct laser writing can be used to prepared integrated optical waveguides as an alternative method to common heat-treatment processes.

Annealing Rate as a Crucial Parameter Controlling the Photoelectrochemical Properties of AuCu Mosaic Core–Shell Nanoparticles

Thermal processing is an essential step during the synthesis of various metal nanostructures and for tailoring their morphology, optical, and electrochemical properties. Herein, a profound impact of the annealing rate and time on photoactivity of gold–copper nanostructures by changes in the position and alignment of energy levels and surface states is reported. AuCu nanoparticles (NPs) are fabricated by sputtering of thin metal layers on the Ti nanopatterned foil followed by slow (0.67 °C s−1) or fast (30 °C s−1) treatment in the rapid thermal annealing furnace and then utilized as photoanodes. Photocurrent in the visible range of the slow‐heated AuCu materials is 77 times higher, whereas for the fast heated 24 times higher than for pure Ti platform. On the other hand, the fast‐heated material exhibits higher photon‐to‐current efficiency, longer recombination rate which reaches 10s, and higher carrier transport rate of 150 μs. Based on the simulated projected local density of states analysis and the characteristics of intensity‐modulated spectra, this phenomenon is attributed to the presence of deeper midgap states in the electronic band structure for the fast‐heated samples. Furthermore, photocurrent is enhanced by the presence of Au inside NPs, which increases tunneling across copper oxides junction.

Temperature-controlled nanomosaics of AuCu bimetallic structure towards smart light management

Gold–copper nanostructures are promising in solar-driven processes because of their optical, photocatalytic and photoelectrochemical properties, especially those which result from the synergy between the two metals. Increasing interest in their internal structure, such as the composition or distribution of the Au and Cu as well as the size and shape of the nanoparticles, have developed to define their physicochemical properties.In this work, we present the influence of thermal treatment in temperature ranges from 100 to 600 °C on the formation process of bimetallic AuCu structures and their properties. AuCu materials were placed on nanostructured titanium foil substrates that were fabricated using electrochemical anodisation and chemical etching. Thin layers of AuCu mixture, as well as Au and Cu, were sputtered on the obtained Ti nanodimples. The materials were then annealed in a rapid thermal annealing furnace in an air atmosphere. Thermal treatment strongly affected the morphology and optical properties of the fabricated materials. AuCu NPs formed at 400 °C in titanium dimples. The material exhibits absorption of visible light in the range from c.a. 400 to 700 nm. The characterisation of the chemical nature of the samples was determined using X-ray photoelectron spectroscopy. In addition, X-ray diffraction and Raman spectroscopy defined composition and crystallinity. Based on photoelectrochemical studies carried out with the use of linear voltammetry in 0.1 M NaOH, it is possible to distinguish two types of interactions of light with the materials such as photogenerated charge accumulation and electron–hole pair separation. A 10AuCu electrode annealed at 300 °C achieved the highest current registered under illumination at − 0.17 V vs. Ag/AgCl/0.1 M KCl. The value was 11 times higher than for a non-annealed structure.

Synthesis and magnetic studies of pure and doped NiZn ferrite films using Sol gel method

In this work, the effect of Co and Cu doping on the magnetic properties of Nickel Zinc ferrite films was investigated. Three types of films with composition Ni0.5Zn0.5Fe2O4, Ni0.35Cu0.2Zn0.45Fe2O4 and Ni0.35Co0.2Zn0.45Fe2O4 were prepared using the sol-gel method. These films were annealed at 500, 600, 700 and 800 °C using a rapid thermal annealing furnace. XRD diffraction confirmed the formation of single-phase spinel structure in these films. Magnetic properties such as saturation magnetization (Ms) and coercivity of these films were measured using an alternating gradient magnetometer. The highest values of Ms were obtained for films annealed at 600 °C which are 350, 334 and 261 emu/cm3 for undoped, Co doped and Cu doped films, respectively. The corresponding coercivity values of these films were 102, 509 and 95 Oe. Thus, Co0.2 doping resulted in an increase in the coercivity whereas Cu0.2 doping reduced the coercivity. Grain size distribution was measured using a scanning electron microscope. It was observed that at higher annealing temperatures (above 600 °C), films developed cracks which results in the reduction of the saturation magnetization from such films.

Electrical, Morphological, and Compositional Characterization of Screen-Printed Al Contacts Annealed in Horizontal and Vertical Configurations

The electrical, morphological, and compositional characteristics of screen-printed Al paste contacts on p-doped Si wafers have been investigated in horizontal and vertical thermal annealing configurations over a wide temperature range. The horizontal configuration refers to an industrial six-zone conveyor belt rapid thermal annealing furnace. The vertical configuration refers to a modified three-zone quartz tube furnace with vertically stacked wafers. The contact resistivity was measured by using the transmission line method. In the horizontal configuration, the resistivity exhibited a pronounced minimum at temperature of ∼ 870°C, while higher temperatures resulted in a rapid increase in the contact resistivity. In contrast, the resistivity variation in the vertical configuration was linear. The lowest contact resistivities measured were 136 mΩ cm2 in the horizontal and 103 mΩ cm2 in the vertical configuration, demonstrating a 24% reduction with the latter approach. The surface morphology and composition of the Al/Si contact interface were determined by field-emission scanning electron microscopy and energy-dispersive x-ray spectroscopy. The measured elemental concentrations were curve-fit to accurately measure the width of the interface regions. The Al/Si contact region was observed to consist of five parts: (a) a top sintered paste layer of Al/Si spheres, (b) voids between the Al/Si spheres, (c) an Al/Si eutectic region, (d) an epitaxially grown Al-doped Si layer, and (e) the lightly Al-diffused Si substrate. Sintered Al/Si spheres were observed to consist of a solid core of Al embedded in a thin shell of Al, Al2O3, SiO2, and Si. The rapid rise in resistivity at high temperatures is attributed to enhanced oxidation of Al and Si islands, resulting in thicker Al2O3/SiO2 films between metallic Al spheres. The lower resistivity observed in the vertical configuration was attributed to larger, more uniform Al–Si eutectic regions, higher density of Al/Si films within the paste region, and transformation of sintered Al spheres into larger pseudosquare islands. The proposed Al/Si interface model was further supported by the higher resistance measured for the pulsed laser-based Al/Si contact with high Si concentrations in the Al/Si eutectic region. An approximately linear reduction in resistivity as a function of time over a broad range varying from microseconds to seconds reinforced the proposed model and suggests that longer, steady-state annealing is the preferred approach to achieve the lowest contact resistivity.

Sol‐gel route to nanocrystalline Eu2Ti2O7 films with tailored structural and optical properties

AbstractWe present a generic sol‐gel approach for the preparation of highly transparent europium titanate Eu2Ti2O7 films with tailored structural and optical properties. The films were prepared by a sol‐gel process and thermally treated in a rapid thermal annealing furnace. We determined the effects of the annealing temperature on structural, morphological, and optical properties of the films. We evaluated film's optical constants. The size of the primary nanocrystals and the film's refractive index were tailored by the annealing temperature. The crystallization of Eu2Ti2O7 started at 800°C and the nanocrystals grew with increasing annealing temperature reaching the size from 20 nm to 100 nm. The energy of nanocrystal growth was 21 ± 3 kJ·mol−1. Increasing nanocrystal size caused the regular growth of the refractive index recorded at 632 nm from 2.07 to 2.17 for the films annealed at 800°C and 1200°C, respectively. These results provide fundamental information about the effects of the structure and the morphology of the films on their optical properties. The presented approach can be extended to other rare earth‐doped titanates and these films can be used as passive protective coatings as well as active materials suitable for photonic and spintronic applications.

The Effect of Substrate Temperature on the Phase Formation of Spray-Pyrolysed Ternary Cu2SnS3 for Thin-Film Solar Cells

The Cu2SnS3 thin films are deposited by spray pyrolysis at different substrate temperatures to ensure the phase purity of the photovoltaic absorber material. No pH controlling agent and complexing agent are used in the preparation. Here, Cu2SnS3 thin films have been deposited with the substrate temperature ranging from 200 to 280 °C for finding the optimum phase formation temperature. From the XRD study it is found that the films deposited at the substrate temperature of 280 °C are pure in phase with uniform deposition throughout the film active area. Subsequently, films are heat-treated in rapid thermal annealing furnace under sulphur atmosphere at 420 °C, which shows increased crystallinity of the tetragonal Cu2SnS3 phase with the preferred orientation along (112) crystal direction. Optical study reveals a bandgap (Eg) of 1.39 eV with the absorption coefficient more than 104 cm−1. The films are p-type semiconductor with the electrical conductivity of 2.5 × 102 S/cm. Our study establishes the potential of the Cu2SnS3 thin films developed using inexpensive spray deposition for photovoltaic applications.

Sol-gel route to highly transparent (Ho0.05Y0.95)2Ti2O7 thin films for active optical components operating at 2 μm

We present a generic sol-gel route to the preparation of optically active nanocrystalline holmium-yttrium titanate (Ho0.05Y0.95)2Ti2O7 thin films, which exhibit a strong luminescence at 2 μm. The films were prepared by the sol-gel process and thermally treated in a rapid thermal annealing furnace. The nanocrystal size and optical properties were tailored by the processing temperature. The final film thickness was around 500 nm. X-ray diffraction analysis and Raman spectroscopy confirmed the high purity of the crystal phase of (Ho0.05Y0.95)2Ti2O7. The activation energy of crystal growth was 35.7 kJ mol−1. The films had excellent structural and surface homogeneity causing their high transparency close to the theoretical limit of 93.39%. Refractive index of the film heat-treated at 1000 °C was around 1.98. The films exhibited strong emission at 2 μm with a luminescence lifetime around 4.6 ms. Their properties together with processing feasibility make them promising materials for photonic applications.

In Situ Arsenic Doping of CdTe/Si by Molecular Beam Epitaxy

p-Type doping of the absorbed layer has been a significant challenge for CdTe solar cells. In this work, we report on in situ arsenic doping of molecular beam epitaxy (MBE) CdTe grown on Si(211) and the use of a cadmium overpressure to enhance incorporation. When growing CdTe:As without a Cd overpressure, extremely high As fluxes are required to achieve noticeable amounts of arsenic incorporation. By supplying a Cd flux during growth, the As incorporation increases by an order of magnitude. By including a Cd overpressure during growth, we have obtained single-crystal CdTe:As films with As incorporation concentration of \(1\times 10^{17} \, \mathrm {\rm cm}^{-3}\). An activation anneal was performed on these films in a rapid thermal annealing furnace, resulting in p-type layers with net carrier concentration of ∼5 × 1016 cm−3.

A Study on the Chemistry of Epitaxial Ti<sub>3</sub>SiC<sub>2</sub> Formation on 4H-SiC Using Al-Ti Annealing

In order to form Ti3SiC2 on 4H-SiC(0001) 8°-off, 200 nm of Ti30Al70 was deposited onto SiC substrates by magnetron sputtering from pure Ti30Al70 targets. The samples were then annealed at 1000°C for 10 min under Ar atmosphere in a Rapid Thermal Annealing (RTA) furnace. Structural analyses reveal the formation of epitaxial hexagonal Ti3SiC2 (0001) oriented. Elemental analyses show that high amount of Al and O elements are present inside the deposit. Obviously, the formation of Ti3SiC2 is accompanied by parasitic Al oxide, probably due to some unwanted oxygen residual in the RTA chamber. By using proper backing steps before the annealing, the deposit is not anymore composed of only Ti3SiC2 but accompanied with other compounds (Al3Ti, and Al). On the oxide-free sample, the specific contact resistance ρc of the Ti3SiC2 based contact on p-type 4H-SiC (having Na= 2×1019 cm-3) was measured to be as low as 6×10-5 Ω.cm2.

Novel chemical process for preparing h-BN solid lubricant coatings on titanium-based substrates for high temperature tribological applications

Hexagonal boron nitride (h-BN) coatings prepared from a polyborazylene (PBN) polymeric precursor were deposited on titanium-based substrates and annealed via infra-red irradiation in a rapid thermal annealing (RTA) furnace. Crystallized h-BN coatings were obtained by adding Li3N as a catalyst at a relatively low annealing synthesized temperature (~1200°C). The resulting coatings had a thickness of 15μm and were evenly coated and homogenous. The coating/substrate adhesion was evaluated by the micro-scratch test, with the value of best critical load occurring at approximately 12N against a Rockwell C diamond point. This adhesion increased with the growth of the additive ratio of Li3N. The friction coefficient measurements were carried-out by tribological testing at 360°C using a cylinder/disk configuration. Stainless steel 15-5PH cylinders were used as counter bodies to the titanium disk. The friction coefficient was reduced from 0.72 for the Ti/stainless tribosystem to 0.35 for the Ti/h-BN/stainless tribosystem.

Structural and electrical properties of 0.1BiYbO3–0.9PbTiO3 piezoelectric thin films grown by pulsed laser deposition

High Curie temperature piezoelectric materials have experienced huge development and widespread application in recent decades, especially for the application of novel perovskite xBiMeO3–(1−x) PbTiO3 solid–solutions family. Nowadays, with the fast increasing applications for integrated ferroelectrics, the high Curie temperature piezoelectric thin films have drawn considerable attention. In this paper we present the works on the preparation and electrical properties of 0.1BiYbO3–0.9PbTiO3 thin films on Pt/TiO2/SiO2/Si (100) substrates by using pulsed laser deposition at 600°C with different oxygen atmosphere pressure. The final samples were post-annealed at 700°C for 10min in a rapid thermal annealing (RTA) furnace. The phase structure and surface morphologies of the 0.1BiYbO3–0.9PbTiO3 thin films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. The frequency dependent dielectric properties were measured by an Agilent4980A LCR meter. Finally, the piezoelectric properties of the films were tested by using piezoelectric force microscopy (PFM).

Effect of a Second Annealing Process on the Properties of BaTiO3 Thin Films on Polycrystalline Nickel Substrates Grown by Polymer-Assisted Deposition

Ferroelectric BaTiO3 thin films were successfully deposited on nickel foils by a chemical solution technique named polymer-assisted deposition. It is found that a second annealing in oxygen using a rapid thermal annealing furnace would strongly affect the electric properties of the as-prepared thin films. Dielectric and ferroelectric properties have been systematically studied. The correlation between the second annealing conditions and dielectric properties was established and discussed. Optimized second annealing condition was found.

Design and Test of a Rapid Thermal Annealing Furnace for Improving Surface Properties of Silicon Brick in Multi-Wire Sawing Process

Multi-wire sawing process with free abrasive slurry or called multi-wire slurry wire sawing (MW-SWS) process has been popularly adopted in slicing of silicon substrates for solar cell application. However, the chipping or edge cracking of thin thickness as 200 μm of such silicon substrates need to be improved in current mass production. The potential subsurface cracks induced by previous edge grinding or brush polishing of silicon brick may be the main cause. This paper is to develop a rapid thermal annealing (RTA) process for thermal annealing of the surface quality of silicon brick before MR-SWS. In this study, a RTA furnace is designed and used to improve the material property of surface of silicon brick. A quartz crucible is used as heating source with the maximum heated specimen size of 156×156×100 mm (W×H×L). The bulk silicon brick used in this study is selected with a size of 20×10×20 mm (W×H×L) and supplied by the Sino-American Silicon Ltd. (SAS) in Hsinchu, Taiwan. The nitrogen gas is also injected as a protective gas for target heating temperature around 550°C with rapid heating rate of 50°C per second. The micro-Vickers (Akashi MVK-H1) and SEM (JSM-6500F, JOEL) instruments have been used to observe the improvement of rectified material properties of bulk silicon substrate. Experiments of silicon wafers have been first performed for obtaining the recipe of RTA testing and then adjusting for silicon brick testing. Results have been verified by the lower surface hardness and larger crystal grain size after RTA treatment. Furthermore, such treated silicon brick can be further adopted for MW-SWS process to identify the effects of reducing chipping or edge cracking of silicon substrates for solar cell application.

Spectral characterization of Mg2Si pn ‐junction diode depending on RTA periods

AbstractWe have studied the effect of thermal annealing periods on the optoelectrical properties of Mg2Si pn ‐junction diodes fabricated by a conventional thermal diffusion process of Ag acceptor. The Au/Ag/n ‐Mg2Si (carrier concentration = 2 × 1015cm‐3, resistivity = 5‐10 Ωcm) substrate was annealed at 550 °C in the Ar‐atmosphere using a rapid thermal annealing (RTA) furnace. The annealing periods were varied between 2 and 10 minutes. Clear rectifying behavior of J ‐V characteristics was observed for the diodes annealed for more than 2 minutes. Spectral responsivity from the photon energy threshold of approximately 0.6 eV was demonstrated with the Mg2Si pn ‐junction diodes under the zero bias condition at room temperature. The maximum intensity of spectral responsivity was increased with decrease the annealing period. The spectral responsivity of the diode with the RTA periods of 4 minutes was approximately 4 times higher than that of 10 minutes annealed one. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Cu2ZnSnSe4 thin film solar cells prepared by rapid thermal annealing of co-electroplated Cu–Zn–Sn precursors

Cu2ZnSnSe4 (CZTSe) thin films were prepared by selenization of co-electrodeposited Cu–Zn–Sn precursors, which were electrodeposited on Mo-coated glass substrates in one-step process. Two annealing processes, rapid thermal annealing (RTA) and conventional furnace annealing (CFA), were carried out for selenizing the precursors at 500°C. The structure and morphology of the CZTSe thin films were characterized using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). It is found that the RTA process benefits the formation of single phase CZTSe absorbers with large grains and the energy band gap of CZTSe film is 0.98eV. Photovoltaic cells with the structure of glass/Mo/CZTSe/CdS/i-ZnO/ZnO:Al were fabricated using the RTA–CZTSe films as absorbers. The highest efficiency of 4.5% so far for a co-electrodeposited CZTSe solar cell was achieved.

Influence of rapid thermal annealing on the process of aluminum induced crystallization of amorphous Si

The effects of annealing methods on the crystallization process and microstructure of polycrystalline silicon (poly-Si) films obtained by aluminum-induced crystallization (AIC) of amorphous Si (a-Si) films were comparatively investigated. Glass/Al/a-Si structures were annealed by rapid thermal annealing (RTA) and conventional furnace at 500 °C for different times in Ar. As compared to furnace annealing, AIC of a-Si films annealed by RTA possesses a shorter period of nucleation time, a higher nucleation density and reduces the process time to form continuous poly-Si films. It is revealed that the continuous Si films obtained by both RTA and conventional furnace annealing are polycrystalline in nature, exhibiting good microstructures with Raman peaks at 518 cm−1 and full-width at half-maximums of 6.43–6.48 cm−1.