Study of SHI induced recrystallization effects in SOI structures synthesized by nitrogen and oxygen ion implantation in silicon

Silicon oxynitride (Si_xO_yN_z) buried insulating layers were synthesized by implantation of nitrogen (¹⁴N⁺) and oxygen (¹⁶O⁺) ions sequentially in the ratio 1:1 at 150 keV to ion-fluences ranging from 1 × 10¹⁷ to 5 × 10¹⁷ cm⁻² to prepare silicon on insulator (SOI) structures. The as implanted samples were held at 270 °C and irradiated to total fluence of 1 × 10¹⁴ cm⁻² by 60 MeV Ni⁺⁵ to study the structural changes/recrystallization of SOI structures induced by swift heavy ion (SHI) irradiation. Fourier transform infrared (FTIR) measurements on the as implanted samples (≤1 × 10¹⁸ cm⁻²) show a single absorption band in the wavenumber range 1300-750 cm⁻¹ attributed to the formation of silicon oxynitride (Si-O-N) bonds in the implanted silicon. It is observed that a nitrogen rich silicon oxynitride structure is formed after SHI irradiation. The study of X-ray rocking curves on the samples show the formation of small silicon crystallites due to swift heavy ion irradiation.     

Simultaneous recrystallization, phosphorous diffusion and antireflection coating of silicon films using laser treatment

Laser technique application to polycrystalline silicon thin-film solar cell fabrication on glass substrates has received appreciable attention. In this paper, a laser-doping technique is developed for plasma-deposited amorphous silicon film. A process involving recrystallization, phosphorous diffusion and antireflection coating can be achieved simultaneously using the laser annealing process. The doping precursor, a phosphorous-doped titanium dioxide (TiO₂) solution, is synthesized using a sol-gel method and spin-coated onto the sample. After laser irradiation, the polycrystalline silicon grain size was about 0.5∼1.0 μm with a carrier concentration of 2 × 10¹⁹ cm^− 3 and electron mobility of 92.6 cm²/V s. The average polycrystalline silicon reflectance can be reduced to a value of 4.65% at wavelengths between 400 and 700 nm, indicating the upper TiO₂ film of antireflection coating.     

Infrared spectra of silicon nanowires

Infrared (IR) spectra of the silicon nanowires (SiNWs) with oxide layer are analyzed by introducing the disorder-induced mechanical coupling between the optically active oxygen asymmetric stretch (AS) and inactive oxygen asymmetric stretch (I-AS) modes in terms of the transverse-optic (TO) and longitudinal-optic (LO) vibrational modes. The shapes of the IR spectra are similar to that of the reported SiO₂, indicating that the SiNWs possess an oxide layer outside. The TO frequencies of coupled AS and I-AS are experimentally observed as peak at approximately 1085 cm^− 1 and its shoulder of 1200 cm^− 1, respectively. The other TO absorption peaks of ∼ 468 cm^− 1, ∼ 480 cm^− 1, and ∼ 808 cm^− 1 are also observed. Furthermore, the intensity of the AS-mode TO band centered at ∼ 1085 cm^− 1 decreases while those of silicon lattice absorption peaks are enhanced with the crystalline quality increased.     

Structural and optical properties of GaN-based nanocrystalline thin films

We study the effect of annealing on structure, morphology and optical properties of nanocrystalline films of GaN, GaN:O and GaN:Mn prepared by ion assisted deposition on silicon, quartz and glassy carbon substrates. Blisters and holes having diameters proportional with the thickness of the film were observed in GaN:O deposited on silicon and glassy carbon. The Mn excess in GaN:Mn turns through annealing into Mn_xN_y islands. The degree of short- and intermediate-range order in the films was investigated by micro-Raman spectroscopy, extending to about 3 nm for gallium oxynitride films annealed to 973 K and to more than 10 nm in GaN samples. A diminished oxygen content following the annealing procedures on GaN:O samples is noticed from the reduced intensity of the oxygen mode at 1000 cm^− 1 in the Raman spectra. This observation is supported with X-ray photoemission spectroscopy measurements. The presence of oxygen at concentrations above 15at.% in the films leads to an abrupt nanocrystalline-amorphous transition.     

Influence of pressure annealing on electrical properties of Mn implanted silicon

The effect of annealing at 610-720 K under enhanced hydrostatic pressure (HP) on electrical properties of manganese implanted Czochralski grown silicon (CzSi:Mn) and floating zone grown silicon (FzSi:Mn) (doses up to 1×10¹⁶ cm⁻¹, E=160 keV) was investigated by electrical C-V, I-V and admittance measurements. Mn⁺ implantation produces both donor-like and acceptor-like implantation-induced defects. The stress-induced decrease in the hole concentration was detected in CzSi implanted by Mn⁺ and annealed at temperatures 610-670 K. The effect of changing initial conductivity of CzSi:Mn samples of high concentration of interstitial oxygen, from p type to n type, due to thermal donors (TDs) generation has been observed. The electron concentration after type conversion depends on annealing conditions and Mn⁺ dose. The TDs generation has not been detected in FzSi:Mn samples containing lower oxygen concentration, however, the FzSi:Mn samples annealed at 720 K under 10⁵ Pa for 10 h indicate at the implanted side the increased carrier concentration due to the defects produced by Mn⁺ implantation. The heat treatment of FzSi:Mn under HP at 720 K for 10 h results in further increase of carrier concentration due to the defect generation.     

Oxide-ion conductivity in CuxCe1−xO2−δ (0 ≤ x ≤ 0.10)

Up to 10 at.% of copper readily substitutes for cerium in ceria. It is found that at oxygen partial pressures between 0.21 atm and 10⁻⁵ atm, Cu_xCe_1−xO_2−δ (0 ≤ x ≤ 0.10) solid solution behave as an oxide-ion electrolyte. Interestingly, Cu_0.10Ce_0.90O_2−δ exhibits the oxide-ion conductivity of ca. 10⁻⁴ Ω⁻¹ cm⁻¹ at 600 °C at an oxygen partial pressure of 10⁻⁵ atm.     

Morphology and phase modifications of MoO3 obtained by metallo-organic decomposition processes

Molybdenum oxide samples were prepared using different temperatures and atmospheric conditions by metallo-organic decomposition processes and were characterized by XRD, SEM and DRS UV/Vis and Raman spectroscopies. Variation in the synthesis conditions resulted in solids with different morphologies and oxygen vacancy concentrations. Intense characteristic Raman bands of crystalline orthorhombic α-MoO₃, occurring at 992 cm⁻¹ and 820 cm⁻¹, are observed and their shifts can be related to the differences in the structure of the solids obtained. The sample obtained under nitrogen flow at 1073 K is a phase mixture of orthorhombic α-MoO₃ and monoclinic β-MoO₃. The characterization results suggest that the molybdenum oxide samples are non-stoichiometric and are described as MoO_x with x < 2.94. Variations in the reaction conditions make it possible to tune the number of oxygen defects and the band gap of the final material.     

Ni-doped vertically aligned zinc oxide nanorods prepared by hybrid wet chemical route

Ni-doped zinc oxide (Ni:ZnO) nanorods were synthesized by incorporating nickel in vertically aligned ZnO nanorods. Ni was evaporated onto ZnO nanorods and the composite structure was subjected to rapid thermal annealing for dispersing Ni in ZnO nanorods. The optical band gap decreased with increasing amount of Ni incorporation. The origin of the photoluminescence peak at ∼ 400 nm was related to the defect levels introduced due to substitution of Ni²⁺ in the Zn²⁺ site with annealing. The Raman spectra indicated the presence of the characteristic peak at ∼ 436 cm^− 1 which was identified as high frequency branch of E₂ mode of ZnO. The Fourier Transformed Infrared spectra indicated the existence of the distinct characteristic absorption peak at 481 cm^− 1 for ZnO stretching modes. Current-voltage characteristics indicated that the current changed linearly with voltage for both the doped and undoped samples.     

Characterization and electrochemical performance of (Ba0.6Sr0.4)1−xLaxCo0.6Fe0.4O3−δ (x = 0, 0.1) cathode for intermediate temperature solid oxide fuel cells

La-doped Ba_0.6Sr_0.4Co_0.6Fe_0.4O_3−δ perovskites were synthesized and investigated as new cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). The structural characteristics, thermal expansion coefficient (TEC), electrical conductivity and electrochemical properties were characterized by X-ray diffraction (XRD), dilatometry, DC four-terminal method, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. The TEC of (Ba_0.6Sr_0.4)_0.9La_0.1Co_0.4Fe_0.6O_3−δ (BSLCF) was 14.9 × 10⁻⁶ K⁻¹ at 30-800 °C, lower than Ba_0.6Sr_0.4Co_0.4Fe_0.6O_3−δ (BSCF) of 15.6 × 10⁻⁶ K⁻¹. The electrical conductivity of BSCF was improved by La-doping, e.g. a value of 122 S cm⁻¹ for BSLCF vs. 52 S cm⁻¹ for BSCF at 500°C, respectively. In addition, La-doping enhanced the electrochemical activity for oxygen reduction reaction. The polarization resistance of BSLCF was 0.18 Ω cm² at 700 °C, about a quarter lower than that of BSCF. The improved electrochemical performance of BSLCF should be ascribed to the higher conductivity as well as the improved oxygen adsorption/desorption and oxygen ions diffusion processes.     

Deterioration and recovery in the resistivity of Al-doped ZnO films prepared by the plasma sputtering

A hot-cathode plasma sputtering technique was used for fabricating the highly transparent and conducting aluminum-doped zinc oxide (AZO) films on glass substrates from a disk-shaped AZO (Al₂O₃: 2 wt.%) target. Under particular conditions where the target voltage was V_T = −200 V and the plasma excitation pressure was P_S = 1.5 × 10⁻³ Torr, the lowest resistivity of 4.2 × 10⁻⁴ Ω cm was obtained at 400 nm, and this was associated with a carrier density of 8.7 × 10²⁰ cm⁻³ and a Hall mobility of 17 cm²/V s. From the annealing experiment of the AZO films in the oxygen and nitrogen gases of the atmospheric pressure it was revealed that both the oxygen vacancies and the grain boundaries in the polycrystalline AZO film played an important role in the electrical properties of the film.     

100 keV nitrogen ion beam implanted polycarbonate: A possibility for UV blocking devices

Polycarbonate samples were implanted with 100 keV N⁺ ions at fluences 10¹⁵, 10¹⁶ and 5 × 10¹⁶ ions cm⁻². Drastic alterations in UV-Visible transmittance spectra were observed which are interrelated with change in surface color and optical absorption of the implanted samples. UV-Visible transmission studies show that at ion fluence of 10¹⁶ ions cm⁻², transmission approaches to zero at about λ = 427 nm and below up to 200 nm. Optical band gap (E_OPT) reduces with increase in fluence and at maximum ion fluence of 5 × 10¹⁶ N⁺ cm⁻², E_OPT was determined to be 1.56 eV whereas for pristine its value was 3.00 eV. Raman analysis indicates the formation of amorphous carbon on the surface of polycarbonate at an ion fluence of 10¹⁶ N⁺ cm⁻². Rise in fluence to 5 × 10¹⁶ N⁺ cm⁻² results in enhancement in disorder on the surface of the host polymer. Modifications in the structural arrangements were found to be in strong association with changes in optical properties with increase in ion fluence and the same is discussed.     

Nanocluster evolution in Ge ion implanted Ta2O5 layers

Ion implantation-induced nanoclusters were synthesized in reactive sputtered Ta₂O₅ films by Ge⁺ implantation and subsequent annealing. The effects of ion fluence and post-implantation thermal treatment on the kinetics of the nanoclustering were investigated. Ge⁺ ions with energy of 40 keV and fluences of 5 × 10¹⁵, 1 × 10¹⁶ and 5 × 10¹⁶ cm^− 2 were implanted in the Ta₂O₅ layers at room temperature. The samples were thermally treated by rapid thermal annealing in vacuum at 700 °C and 1000 °C for 30, 60 and 180 s. Structural studies of all samples were done by Cross-sectional Transmission Electron Microscopy in diffraction and phase contrast mode. Under optimized conditions (high implantation fluence, subsequent annealing) nanoclusters are formed around the projected ion range of the implanted Ge⁺ ions. The structure of the implanted Ta₂O₅ matrix changes from amorphous to orthorhombic when the annealing was performed at 1000 °C. Although the Ta₂O₅ matrix crystallizes, no evidence is obtained for crystallization of the embedded nanoclusters even after annealing at 1000 °C.     

Protonic conduction in Ca-doped La2M2O7 (M = Ce, Zr) with its application to ammonia synthesis electrochemically

Complex oxides La_1.95Ca_0.05M₂O_7−δ (M = Ce, Zr) were prepared by sol-gel method and characterized by thermal analysis (TG-DTA), X-ray diffraction (XRD). On the sintered complex oxides as solid electrolyte, the conductivity was measured in various atmospheres, and ammonia was synthesized from nitrogen and hydrogen at atmospheric pressure in the solid states proton conducting cell reactor by electrochemical methods. The rates of ammonia formation were up to 2.0 × 10⁻⁹ mol s⁻¹ cm⁻² for La_1.95Ca_0.05Zr₂O_7−δ and 1.3 × 10⁻⁹ mol s⁻¹ cm⁻² for La_1.95Ca_0.05Ce₂O_7−δ, respectively, at 520 °C.     

Annealing behavior of single mode planar waveguide in YVO4 produced by He ion implantation

We report, for the first time to our knowledge, the formation of single mode planar waveguide in z-cut YVO₄ by 400 keV, 500 keV He ion implantation in fluence of 3 × 10¹⁶ ions/cm² at room temperature or at liquid nitrogen temperature (77 K). We investigated annealing behavior of the guiding mode and near-field image in the waveguide by prism-coupling method and end-face coupling method respectively. We found that the effective refractive index of the TE₀ mode was different before and after annealing for the samples implanted at room temperature, while, annealing had nearly no influence on the effective refractive index of the TE₀ mode of the samples implanted at liquid nitrogen temperature (77 K). After annealing at 600 K for 1 h, no guiding mode was observed in the sample implanted by 400 keV He ion in fluence of 3 × 10¹⁶ ions/cm² at room temperature. The Rutherford backscattering/channeling technique was used to investigate the damage reduction after annealing treatments. The minimum yield of the implanted, annealed sample was 5.43%. We reconstructed the refractive index profiles in the waveguide under different condition by applying intensity calculation method.     

Diffusion of Pb in carbon ion-implanted silicon: Discovery of a new crystalline phase after electron beam annealing

A novel phase has been discovered by dual low-energy ion implantation and high vacuum electron beam annealing. (100) p-type Si was implanted with (a) 20 keV ¹²C⁺ ions to the fluence of 6 × 10¹⁶ cm⁻² and (b) 7 keV Pb⁺ ions to the fluence of 4 × 10¹⁵ cm⁻². The ¹²C ion implantation results in an understoichiometric shallow SiC_x layer that intersects with the surface. The implanted Pb ions decorate a shallow subsurface region. High vacuum electron beam annealing at 1000 °C for 15 s using a temperature gradient of 5 °C s⁻¹ leads to the formation of large SiC nanocrystals on the surface with RBS measurements showing Pb has diffused into the deeper region affected by the ¹²C implantation. In this region, a new crystalline phase has been discovered by XRD measurements.     

Dielectric and ferroelectric properties of Ba(Sn0.15Ti0.85)O3 thin films grown by a sol-gel process

Ferroelectric Ba(Sn_0.15Ti_0.85)O₃ (BTS) thin films were deposited on LaNiO₃-coated silicon substrates via a sol-gel process. Films showed a strong (1 0 0) preferred orientation depending upon annealing temperature and concentration of the precursor solution. The dependence of dielectric and ferroelectric properties on film orientation has been studied. The leakage current density of thin films at 100 kV/cm was 7 × 10⁻⁷ A/cm² and 5 × 10⁻⁵ A/cm² and their capacitor tunability was 54 and 25% at an applied field of 200 kV/cm (measurement frequency of 1 MHz) for the thin films deposited with 0.1 and 0.4 M spin-on solution, respectively. This work clearly reveals the highly promising potential of BTS compared with BST films for application in tunable microwave devices.     

High performance low temperature solution-processed zinc oxide thin film transistor

Amorphous zinc oxide thin films have been processed out of an aqueous solution applying a one step synthesis procedure. For this, zinc oxide containing crystalline water (ZnO⋅ × H₂O) is dissolved in aqueous ammonia (NH₃), making use of the higher solubility of ZnO⋅ × H₂O compared with the commonly used zinc oxide. Characteristically, as-produced layers have a thickness of below 10 nm. The films have been probed in standard thin film transistor devices, using silicon dioxide as dielectric layer. Keeping the maximum process temperature at 125 °C, a device mobility of 0.25 cm²V^− 1s^− 1 at an on/off ratio of 10⁶ was demonstrated. At an annealing temperature of 300 °C, the performance could be optimized up to a mobility of 0.8 cm²V^− 1s^− 1.     

Low turn-on and high efficient oxidized amorphous silicon nitride light-emitting devices induced by high density amorphous silicon nanoparticles

The role of amorphous silicon nanoparticles (a-Si NPs) in electroluminescent characteristics of oxidized amorphous silicon nitride (a-SiN_x:O) light-emitting devices (LEDs) has been studied. A-Si NPs with a high density of 1 × 10¹² cm^− 2 are formed in the a-SiN_x:O films after rapid thermal annealing at 900 °C for 40 s. A notably enhanced electroluminescence (EL) is obtained from the a-Si-in-SiN_x:O devices and the EL peak position can be tuned from red to green-yellow by controlling the forward voltage. Compared to EL of the a-SiN_x:O device, the turn-on voltage can be reduced to 3 V and the EL power conversion efficiency can be almost six times higher. The improved performance of the LEDs is ascribed to the effective carrier injection due to introduction of high density a-Si NPs.     

Effect of reactive gases flow ratios on the microstructure and electrical resistivity of Ta-N-O thin films by reactive co-sputtering

A combination of the beneficial properties of tantalum oxide and tantalum nitride may result in a new and functional tantalum oxynitride (Ta-O-N). In this paper, Ta-O-N thin films were fabricated by using reactive magnetron sputtering at different reactive gas ratios. The ratio of reactive gases to total flow gases was controlled from 6% to 30%. The microstructure, composition, chemical bonding, morphology and resistivity of the Ta-O-N thin films were characterized. Increasing reactive gas flow ratio will result in the increase of the O/(O + N) ratio in Ta-O-N from 0.22 to 0.79. All films were quasi-amorphous structures in this study. The higher reactive gas flow ratio led to more disorder or amorphous microstructure with a broader diffraction peak. The position of the highest intensity peak about 36° shifts downward with increasing O/(O + N) ratio because of the sufficient Ta-O phase formation. The FTIR absorption bands at 500-800 cm^− 1 corresponding to Ta-O-Ta and Ta-O stretching vibration modes were observed_. A weak absorption band at 800-1000 cm^− 1 was the tantalum suboxides. The resistivity increased from 288 μΩcm (conducting) to 11,540 Ωcm (semiconducting-insulating) with increasing O/(O + N) ratio. The oxygen content dominates the microstructure formation and resistivity of the Ta-O-N system compared to nitrogen.     

Activation behavior of boron implanted poly-Si on glass substrate

The activation behavior of boron (B) implanted poly-Si films on glass substrates has been investigated. The effect of B dose and annealing temperature on crystal defects and electrical properties of the films were evaluated by Raman spectroscopy and Hall measurement. It was found that the maximum activation ratio of the film with B dose of 1 × 10¹⁵ cm^− 2 was obtained when Raman peak associated with disordered amorphous silicon disappeared. However, reverse anneal was observed in the film when the annealing temperature further increased. The results from secondary ion mass spectrometry and Hall measurement revealed that B segregation at the top and bottom interface and deactivation of B substitutional occurred simultaneously in the high-dose specimens when the annealing temperature increased from 600 to 750 °C.