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Thickness-modulated optical dielectric constants and band alignments of HfOxNy films grown by sputtering have been investigated by spectroscopic ellipsometry (SE) and x-ray photoelectron spectroscopy. Based on SE measurements, it has been noted that an increase in optical dielectric constant and band gap has been observed as a function of the film thickness. Analyses of thickness-dependent band alignment of the HfOxNy/Si system indicate that the valence band offset increases, but only slight change in the conduction band offset, resulting from the thickness-induced change in the structure. The suitable optical dielectric constants and band offsets relative to Si make sputtering-derived HfOxNy film a promising candidate for high-k gate dielectrics. [ABSTRACT FROM AUTHOR]

N-doped ZnO films were prepared by annealing zinc oxynitride films deposited by rf reactive sputtering. Two Raman peaks were observed at 274 and 580 cm-1. According to the variation of the integral intensity of these two peaks, the nitrogen activation at 500 °C [the activation temperature (AT)] has been obtained. Below the AT, the integral intensities of them show a different variation trend. X-ray photoelectron spectroscopy (XPS) indicates the N chemical state variation for them and finds the activated Zn-N bond. Further analyses by photoluminescence (PL) spectra and spectroscopic ellipsometry (SE) have been carried out. The activated sample exhibits a symmetric emission peak at 3.22 eV assigned to be the A0X emission at room temperature. SE investigation takes account of samples within the different temperature span divided by the AT. Different factors, such as nitrogen dopant (N)O and the nanocrystal growth, which affect the redshift of the absorption edges, have been discussed. [ABSTRACT FROM AUTHOR]

The structural stability and optical properties of ultrathin HfAlOx films grown by facing-target reactive sputtering, depending on the postannealing temperature, have been determined via x-ray photoelectron spectroscopy and spectroscopic ellipsometry (SE). By virtue of the chemical shifts of Hf4f, Al2p, and Si2p core-level spectra, it has been found that the structural stability of HfAlOx/Si system sustains up to 800 °C. However, the breaking of the Hf–Al–O bond and the phase separation take place drastically at the annealing temperature of 900 °C. In particular, the information of an interfacial Si–O–Si bond as the dominant reaction during the postannealing treatment has been observed, confirmed by Fourier transform infrared spectroscopy. Analysis by SE, based on the Tauc-Lorentz model, has indicated that increase in the refractive index and reduction in thickness has been observed as a function of annealing temperature, originating from the annealing-induced higher packing density. The change of the complex dielectric functions and bandgap Eg correlated with the annealing temperature are discussed in detail. [ABSTRACT FROM AUTHOR]

The microstructure and optical dielectric constants of HfOxNy thin films deposited by using radio frequency reactive magnetron sputtering have been investigated at various substrate temperatures. Fourier transform infrared spectroscopy spectra indicate that an interfacial layer has been formed between the Si substrate and the HfOxNy thin film during deposition. Spectroscopy ellipsometry (SE) results show that the substrate temperature has a strong effect on physical properties of HfOxNy thin films such as refractive index n and extinction coefficient k. Meanwhile, the optical dielectric functions of the films have determined using SE data and optical absorption properties of HfOxNy thin films deposited at different substrate temperatures have also been studied. [ABSTRACT FROM AUTHOR]

Presents information on a study that investigated solid phase epitaxy amorphous Sn[subx]Ge[sub1-x] films on strain relieved germanium films on silicon(001) substrates. Experimental procedure; Results and discussion on the study; Conclusions.

Provides information on a study that generated nonsynchronous change of temperature rise and thermal expansion in thin films using transient laser pulse. Experimental procedures; Results and discussion on the study; Conclusion.

The microstructure, optical and electrical properties of HfTiO high-k gate dielectric thin films deposited on Si substrate and quartz substrate by RF magnetron sputtering have been investigated. Based on analysis from x-ray diffraction (XRD) measurements, it has been found that the as-deposited HfTiO films remain amorphous regardless of the working gas pressure. Meanwhile, combined with characterization of ultraviolet-visible spectroscopy (UV–vis) and spectroscopy ellipsometry (SE), the deposition rate, band gap and optical properties of sputtered HfTiO gate dielectrics were determined. Besides, by means of the characteristic curves of high frequency capacitance–voltage ( C – V ) and leakage current density–voltage ( J – V ), the electrical parameters, such as permittivity, total positive charge density, border trap charge density, and leakage current density, have been obtained. The leakage current mechanisms are also discussed. The energy band gap of 3.70 eV, leakage current density of 1.39×10 −5 A/cm 2 at bias voltage of 2 V, and total positive charge density and border trap charge density of 9.16×10 11 cm −2 and 1.3×10 11 cm −2 , respectively render HfTiO thin films deposited at 0.6 Pa, potential high-k gate dielectrics in future CMOS devices. [ABSTRACT FROM AUTHOR]

The effect of oxygen partial pressure on the microstructure, wettability, optical and electrical properties of sputtering-derived HfO 2 thin films has been systematically investigated by using x-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), atomic force microscope (AFM), UV–visible spectroscopy (UV–Vis), spectroscopy ellipsometry (SE), and electrical measurements. XRD results have shown that the HfO 2 thin films are all polycrystalline with monoclinic phase. Based on analysis from FTIR, a strong absorption peak centered at 1105 cm −1 has been detected, indicating the formation of the interfacial layer. Reduction in particle size and decrease in root mean square (RMS) roughness of the HfO 2 thin films have been detected by SEM and AFM measurements with the increase in oxygen partial pressure. Meanwhile, the contact angle decreases and the wettability increases with increasing the oxygen partial pressure. Combined with UV–vis and SE, the optical function of HfO 2 thin films as functions of oxygen partial pressure has been determined. By means of electrical measurements, evolution of electrical performance of MOS capacitor based on HfO 2 gate dielectrics related with oxygen partial pressure has been investigated systematically. [ABSTRACT FROM AUTHOR]

The effect of deposition temperature on the growth rate, band gap energy and electrical properties of HfO 2 thin film deposited by atomic layer deposition (ALD) has been investigated. By means of characterization of spectroscopy ellipsometry and ultraviolet–visible spectroscopy, the growth rate and optical constant of ALD-derived HfO 2 gate dielectrics are determined precisely. The deposition temperature dependent electrical properties of HfO 2 films were determined by capacitance–voltage ( C – V ) and leakage current density–voltage ( J – V ) measurements. The leakage current mechanism for different deposition temperature has been discussed systematically. As a result, the optimized deposition temperature has been obtained to achieve HfO 2 thin film with high quality. [ABSTRACT FROM AUTHOR]

In current report, X-ray photoelectron spectroscopy has been pursued to obtain the valence band discontinuity (Δ E v ) of sputter deposited HfTiO/InZnGaO 4 (IGZO) heterostructures. A Δ E v value of 0.32 ± 0.1 eV was obtained by using the Ga 2p3/2, Zn 2p3/2, and In 3d5/2 energy levels as references. Taking into consideration the experimental band gaps of 5.35 eV and 3.39 eV for HfTiO and IGZO thin films measured by absorption method, respectively, this would result in a conduction band offset of 1.64 eV in this heterostructure. [ABSTRACT FROM AUTHOR]

The optical properties, interface chemistry and band alignment of Hf 1− x Ti x O 2 ( x = 0.03, 0.08, 0.12 and 0.20) high- k gate dielectric thin films, deposited by RF sputtering on Si substrate, have been systematically investigated. The effect of TiO 2 incorporation on the interfacial chemical structure and energy-band discontinuities has been investigated by using X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible spectroscopy (UV–vis). It has been found that the band gap and band offsets of the Hf 1− x Ti x O 2 thin film decrease with the increase of TiO 2 concentration. Meanwhile, the obtained band offsets are all over 1 eV. Thin film capacitors fabricated with the MOS configuration of Al/Hf 1− x Ti x O 2 /n-Si/Al exhibits excellent electrical properties with low interface state density, hysteresis voltage and low leakage current density. The suitable band gap, symmetrical band offsets relative to Si and prominent electrical properties render sputtering-derived Hf 1− x Ti x O 2 with 9% TiO 2 films as promising candidates for high- k gate dielectrics. [ABSTRACT FROM AUTHOR]

Highlights: [•] Sputtering-derived Hf1−xTi x O2 gate dielectrics have been deposited on Si substrates. [•] Increase in crystallization temperature and reduction in Eg have been observed. [•] Formation of silicate layer for 9% TiO2-doped HfO2/Si sample has been detected. [ABSTRACT FROM AUTHOR]

High-k gate dielectric HfO thin films have been deposited on Si and quartz substrates by radio frequency magnetron sputtering. The structural characteristics, surface morphology, and optical properties of the HfO/Si gate stacks at various post-annealing temperatures were examined by X-ray diffraction (XRD), atomic force microscopy (AFM), fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis spectroscopy), and spectroscopic ellipsometry (SE). XRD measurement indicates that the 80 W-deposited HfO films demonstrate a polycrystalline structure. AFM measurements illustrate that the root mean square of the HfO thin films demonstrates an apparent increase with increasing the annealing temperature. Analysis from FTIR indicates that the Si-O-Si bonds vibration peak position shift toward lower wave numbers with increasing the annealing temperature. Combined with UV-Vis spectroscopy and SE measurements, it can be noted reduction in band gap with an increase in annealing temperature has been confirmed. Additionally, increase in refractive index ( n) has been confirmed by SE. [ABSTRACT FROM AUTHOR]

Abstract: Tin dioxide thin films were prepared successfully by pulsed laser deposition techniques on glass substrates. The thin films were then annealed for 30min from 50°C to 550°C at 50°C intervals. The influence of the annealing temperature on the microstructure and optical properties of SnO2 thin films was investigated using X-ray diffraction, optical transmittance and reflectance measurements. Various optical parameters, such as optical band gas energy, refractive index and optical conductivity were calculated from the optical transmittance and reflectance data recorded in the wavelength range 300–2500nm. We found that the SnO2 thin film annealed at temperatures up to 400°C is a good window material for solar cell application. Our experimental results indicated that SnO2 thin films with the high optical quality could be synthesized by pulsed laser deposition techniques. [Copyright &y& Elsevier]

Abstract: ZnO films were prepared by a modified water-based Pechini method where ethanol was added to avoid some disadvantages of solely water-based precursor solution. The ratio of ethanol to water (E/W) largely influences the quality of films, and the appropriate ratio is about 1.2. FT-IR spectra show that the addition of ethanol largely promotes the esterification reaction in the dried gel. XRD results show that all films are of wurtzite structure while the annealing temperature is not higher than 700°C. The secondary phase Zn2SiO4 was found in the films annealed at 800°C because of the reaction between SiO2 substrate and ZnO film. SEM photographs show that all films consist of nanocrystalline grains with sizes in the range of 25–82nm, and the addition of ethanol improves the growth of grains. Transmittance spectra reveal that all films have high average transmittance of about 90% in the range of 450–800nm except those annealed at 800°C. The average optical band gap of films is about 3.29eV. [Copyright &y& Elsevier]

Abstract: Effects of variation of the oxygen partial pressure on the structural and optical properties of zinc oxide (ZnO) thin films prepared by reactive radio-frequency sputtering were investigated. Measurements by X-ray diffraction (XRD) and atomic force microscopy (AFM) indicated that the crystallinity and the surface morphology were sensitive to the oxygen partial pressure. The interfacial and optical properties of the targeted films were investigated by spectroscopic ellipsometry (SE) characterization. Based on Tauc-Lorentz (TL) model, the optical constants of ZnO films were tentatively extracted in the photon energy ranging from 1.5 to 6.0eV. Analyses by XRD and SE revealed that the oxygen partial pressure had effect on the orientation of the ZnO films, the surface morphology, the packing density, and the interfacial layers. And the relationship between crystallinity and interfacial layer, as well as the relationship between surface roughness and packing density was discussed. All these had a significant impact on the optical properties illustrated by SE analysis. [Copyright &y& Elsevier]

Abstract: High-k HfO x N y thin films with different nitrogen-incorporation content have been fabricated on Si (100) substrate by means of radio-frequency reactive sputtering method. Analyses from X-ray diffraction (XRD) and atomic force microscopic have indicated that the increase of the crystallization temperature of HfO2 thin films and the decrease of the roughness root-mean-square value of HfO2 thin films due to the incorporation of nitrogen. Based on a parameterized Tauc–Lorentz (TL) dispersion model, the optical properties of the HfO x N y thin films related to different nitrogen-incorporation content are systematically investigated by spectroscopic ellipsometer. Increase in the refractive index and the extinction coefficient and reduction in band gap with increase of nitrogen-incorporation content are discussed in detail. [Copyright &y& Elsevier]

Abstract: High-k gate dielectric HfO2 thin films have been deposited on Si(100) by using plasma oxidation of sputtered metallic Hf thin films. The optical and electrical properties in relation to postdeposition annealing temperatures are investigated by spectroscopic ellipsometry (SE) and capacitance–voltage (C–V) characteristics in detail. X-ray diffraction (XRD) measurement shows that the as-deposited HfO2 films are basically amorphous. Based on a parameterized Tauc–Lorentz dispersion mode, excellent agreement has been found between the experimental and the simulated spectra, and the optical constants of the as-deposited and annealed films related to the annealing temperature are systematically extracted. Increases in the refractive index n and extinction coefficient k, with increasing annealing temperature are observed due to the formation of more closely packed thin films and the enhancement of scattering effect in the targeted HfO2 film. Change of the complex dielectric function and reduction of optical band gap with an increase in annealing temperature are discussed. The extracted direct band gap related to the structure varies from 5.77, 5.65, and 5.56eV for the as-deposited and annealed thin films at 700 and 800°C, respectively. It has been found from the C–V measurement the decrease of accumulation capacitance values upon annealing, which can be contributed to the growth of the interfacial layer with lower dielectric constant upon postannealing. The flat-band voltage shifts negatively due to positive charge generated during postannealing. [Copyright &y& Elsevier]

Abstract: High-k HfO2–Al2O3 composite gate dielectric thin films on Si(100) have been deposited by means of magnetron sputtering. The microstructure and interfacial characteristics of the HfO2–Al2O3 films have been investigated by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and spectroscopic ellipsometry (SE). Analysis by XRD has confirmed that an amorphous structure of the HfO2–Al2O3 composite films is maintained up to an annealing temperature of 800°C, which is much higher than that of pure HfO2 thin films. FTIR characterization indicates that the growth of the interfacial SiO2 layer is effectively suppressed when the annealing temperature is as low as 800°C, which is also confirmed by spectroscopy ellipsometry measurement. These results clearly show that the crystallization temperature of the nanolaminate HfO2–Al2O3 composite films has been increased compared to pure HfO2 films. Al2O3 as a passivation barrier for HfO2 high-k dielectrics prevents oxygen diffusion and the interfacial layer growth effectively. [Copyright &y& Elsevier]

Abstract: The thermal stability and structural characteristics for gate stack structure of HfO2 dielectrics grown by DC reactive magnetron sputtering were investigated. The structural characteristics and chemical states of the HfO2 films in relation to the postannealing temperature were examined by X-ray diffraction and X-ray photoelectron spectroscopy. XRD patterns demonstrate that the as-grown HfO2 films are amorphous and the structure of the annealed HfO2 films undergoes a transformation of tetragonal to monoclinic phase with increasing annealing temperature and forms a polycrystalline structure at high annealing temperature. Analysis of XPS of Hf4f and O1s gives evidence that the as-grown HfO2 film is nonstoichiometric. With increase of annealing temperature, both peaks of Hf4f and O1s keep on shifting towards lower binding energy, which indicates to be forming stoichiometric HfO2 film. Annealing the as-grown thin film at low temperature leads to the formation of silicate at the interfacial regime resulting from the reaction between the nonstoichiometric thin film and parts of SiOx formed at the interfacial regime, and the Si–O–Hf and Si–O bonds in the silicate and SiOx attributes greatly to the XPS O1s peaks. High temperature annealing process, the O-deficient HfO2 films will absorb oxygen atoms from the formed silicate interfacial layer and the oxygen ambient to form the fully oxidized HfO2 thin films. [Copyright &y& Elsevier]

The effect of nitrogen atom doping on the optical properties and dielectric constant of HfO2 films has been systematically investigated. Spectroscopic ellipsometry was employed to investigate the optical properties of nitrogen incorporated HfO2 films. The values of average oscillator strength and average oscillator position extracted from spectroscopic ellipsometry demonstrated that nitrogen incorporation could influence the dipole oscillator strength and oscillator position of HfO2. A physical model of dipole structures was proposed to verify the enhancement of dielectric constant of HfO2 films by nitrogen incorporation. [ABSTRACT FROM AUTHOR]

Effects of nitrogen incorporation on interfacial property, band gap, and band alignments of high-k Y2O3 gate dielectrics have been investigated. It was found that the incorporation of nitrogen into Y2O3 films can effectively suppress the growth of the interfacial layer between Y2O3 and Si substrate. The incorporation of nitrogen into Y2O3 films leads to the reduction of band gap and valence band offset, but not the conduction offset of Y2O3 films. High temperature annealing will help to increase the band gap and valence band offset of YOxNy film due to the release of the interstitial N atoms. [ABSTRACT FROM AUTHOR]

Temperature-dependent interfacial chemical bonding states and band alignment of HfOxNy/SiO2/Si gate stacks have been investigated by X-ray photoemission spectroscopy (XPS) and spectroscopic ellipsometry (SE). By means of the chemical shifts of Hf 4f, Si 2p, O 1s, and N 1s core-level spectra, it has been found that the chemical stability of the HfOxNy/SiO2/Si stacks strongly depends on the annealing temperature. Analysis of temperature-dependent band alignment of HfOxNy/SiO2/Si stacks suggests that the valence band offset ΔEv increases slowly from 1.82 eV for as-grown film to 2.55 eV for annealed film at 700 °C; however, the values of conduction band offset ΔEc only demonstrates a slight change in the vicinity of 1.50 eV. From the band offset viewpoint, HfOxNy/SiO2/Si gate stack could be a promising candidate for high-k gate dielectrics. [ABSTRACT FROM AUTHOR]

We report in this letter that Hafnium oxynitride (HfOxNy) gate dielectrics were prepared by radio frequency (RF) reactive magnetron sputtering and optical properties of the HfOxNy thin films were investigated by spectroscopic ellipsometry with photon energy of 0.75–6.5 eV at room temperature. The investigations showed that the annealing temperatures have a strong effect on the optical properties of HfOxNy thin films. With increased annealing temperature, the refractive index n is observed to increase, while the extinction coefficient k decreases, respectively. The changes of the complex dielectric functions and the optical band gap Eg with the annealing temperature are also discussed. [ABSTRACT FROM AUTHOR]

Spectroscopic ellipsometry with photon energy 0.75–6.5 eV at room temperature has been used to derive the optical properties of nitrogen-incorporated HfO2 films on Si(100) substrates grown by radio-frequency reactive sputtering using different N2/(N2+O2+Ar) gas ratios from 20% to 50%. Excellent agreement has been found between the experimental and the simulated spectra, in which an empirical dielectric dispersion relation based on Tauc-Lorentz model has been successfully adopted. Increases in the refractive index n and the extinction coefficient. k, with increases in nitrogen-incorporation content are observed due to the nitrogen-incorporation-induced higher packing density. The change of the complex dielectric functions and reduction in the optical band gap with an increase in nitrogen concentration resulting from the effect of the nitrogen-incorporation on the structure are discussed in detail. [ABSTRACT FROM AUTHOR]

Abstract: ZnO thin films on fused quartz substrates were prepared by a glycol-based Pechini method. The structural and optical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), optical transmittance spectrum, and photoluminescence (PL) spectrum. A red emission around 700 nm was found in PL spectrum, and its peak intensity gained a strong enhancement (∼140%) while annealing temperature increased from 700 °C to 800 °C. The red emission was ascribed to the possible high defect density in boundary layers of nanocrystalline grains. [Copyright &y& Elsevier]

Abstract: Spectroscopic ellipsometry (SE) with photon energy 0.75–6.5eV at room temperature has been used to derive the optical properties of high-k ZrO2 thin films on Si(100) substrates prepared by nitrogen-assisted, direct current reactive magnetron sputtering. The Tauc–Lorentz dispersion method was adopted to model the optical dispersion functions of the thin films as a function of annealing temperature. Excellent agreement has been found between the SE fitting results and X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) results, indicating that our model adequately described the measured SE data. Optical band gaps (E g) were also obtained based on the extracted absorption edge. Our results suggest that nitrogen-assisted process can effectively limit the interfacial layer growth in high-k oxides. [Copyright &y& Elsevier]

Abstract: High-k HfO x N y thin films have been grown by radio frequency (rf) reactive sputtering of metal Hf target in N2/Ar/O2 ambient at different substrate temperatures. The chemical compositions of the films have been investigated as a function of substrate temperature by X-ray photoelectron spectroscopy (XPS). XPS measurements showed that nitrogen concentration increases with an increase in substrate temperature. Room-temperature spectroscopic ellipsometry (SE) with photon energy 0.75–6.5eV was used to investigate the optical properties of the films. SE results demonstrated that refractive index n increases with an increase in substrate temperature. Based on TL parameters which were obtained from the best fit results used in a simulation of the measured spectra, meanwhile, we conclude that the energy band gap (E g) decreases with an increase in substrate temperature. [Copyright &y& Elsevier]

Abstract: ZrO2 dielectric films were deposited on Si substrates by reactive magnetron sputtering technique. Interfacial and optical properties were investigated. Crystal structure was studied by X-ray diffraction. Fourier Transform Infrared Spectroscopy analysis confirmed the presence of a low-k interfacial SiO2 layer due to the excited oxygen radicals in the sputtering plasma and the physisorbed oxygen in as-deposited ZrO2 films. Optical constants were extracted based on the best spectroscopic ellipsometry fitting results. Absorption coefficients near the absorption edge were also calculated. The absorption tails in the range 4.5–4.75 eV indicated that there was a defect energy level below the conduction band of ZrO2 due to oxygen vacancies. [Copyright &y& Elsevier]

Abstract: Y2O3 thin film waveguides were prepared by RF magnetron sputtering. The effects of post-deposition annealing on the structure and optical properties have been investigated. The structural evolution of Y2O3 films with annealing temperature was investigated by X-ray diffraction (XRD). Spectroscopic ellipsometry was employed to determine the optical properties of Y2O3 films annealed at various temperatures. It was found that with increasing annealing temperature, the refractive index (n) of Y2O3 films increases. The optical band gap of Y2O3 films shifts to higher energy after higher temperature annealing, which is likely due to the reduction of defects and the change of crystalline structure in Y2O3 films. [Copyright &y& Elsevier]