首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Hafnium oxynitride (HfOxNy) gate dielectric has been deposited on Si (1 0 0) by means of radio frequency (rf) reactive sputtering using directly a HfO2 target in N2/Ar ambient. The thermal stability and microstructural characteristics for the HfOxNy films have been investigated. XPS results confirmed that nitrogen was successfully incorporated into the HfO2 films. XRD analyses showed that the HfOxNy films remain amorphous after 800 °C annealing in N2 ambient. Meanwhile the HfOxNy films can also effectively suppress oxygen diffusion during high temperature annealing and prevent interface layer from forming between HfOxNy films and Si substrates. AFM measurements demonstrated that surface roughness of the HfOxNy films increase slightly as compared to those pure HfO2 films after post deposition annealing. By virtue of building reasonable model structure, the optical properties of the HfOxNy films have been discussed in detail.  相似文献   

2.
ZrOxNy thin films have been prepared by radio frequency magnetron sputtering at various substrate temperatures. The effect of substrate temperature on structural, optical properties and energy-band alignments of as-deposited ZrOxNy thin films are investigated. Atomic force microscopy results indicate the decreased root-mean-square (rms) values with substrate temperature. Fourier transform infrared spectroscopy spectra indicate that an interfacial layer has been formed between Si substrate and ZrOxNy thin films during deposition. X-ray photoelectron spectroscopy and spectroscopy ellipsometry (SE) results indicate the increased nitrogen incorporation in ZrOxNy thin films and therefore, the decreased optical band gap (Eg) values as a result of the increased valence-band maximum and lowered conduction-band minimum.  相似文献   

3.
In the present paper, we investigate the effect of thermal annealing on optical and microstructural properties of HfO2 thin films (from 20 to 190 nm) obtained by plasma ion assisted deposition (PIAD). After deposition, the HfO2 films were annealed in N2 ambient for 3 h at 300, 350, 450, 500 and 750 °C. Several characterisation techniques including X-ray reflectometry (XRR), X-ray diffraction (XRD), spectroscopic ellipsometry (SE), UV Raman and FTIR were used for the physical characterisation of the as-deposited and annealed HfO2 thin films. The results indicate that as-deposited PIAD HfO2 films are mainly amorphous and a transition to a crystalline phase occurs at a temperature higher than 450 °C depending on the layer thickness. The crystalline grains consist of cubic and monoclinic phases already classified in literature but this work provides the first evidence of amorphous-cubic phase transition at a temperature as low as 500 °C. According to SE, XRR and FTIR results, an increase in the interfacial layer thickness can be observed only for high temperature annealing. The SE results show that the amorphous phase of HfO2 (in 20 nm thick samples) has an optical bandgap of 5.51 eV. Following its transition to a crystalline phase upon annealing at 750 °C, the optical bandgap increases to 5.85 eV.  相似文献   

4.
An epitsucial γ-Mg2SiO4 thin film can be a good buffer between the Si substrate and some oxide thin films. For high temperature superconducting multilayer structures, hopefully it can be taken as an insulating layer to replace the widely used MgO film. To explore such possibilities, we carry out systematic studies on the influences of pressure and substrate temperature on the epitaxy of γ-Mg2SiO4 thin films grown on Si (100) substrates using rf magnetron sputtering with an Mg target of purity of 99.95 percent. With the substrate temperature kept at 500℃ and the pressure changing from lO Pa to 15 Pa, in the XRD spectra the 7-Mg2SiO4 (400) peak grows drastically while the MgO (200) peak is suppressed. Keeping the pressure at 15Pa and increasing the temperature from 500℃ to 570℃ further can improve the film epitaxy, while working at 780℃ and 11Pa seems to give very good results. X-ray photoelectronic spectroscopy and φ scan are used to characterize the stoichiometry, crystallinity, and in-plane growth of the samples.  相似文献   

5.
M. Liu  G. He  Q. Fang  G.H. Li 《Applied Surface Science》2006,252(18):6206-6211
High-k HfO2-Al2O3 composite gate dielectric thin films on Si(1 0 0) 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.  相似文献   

6.
Ba(ZrxTi1−x)O3 (BZT) (x = 0.20 and 0.30) thin films are deposited on Pt(1 1 1)/Ti/SiO2/Si(1 0 0) substrate by sol-gel method. X-ray diffraction patterns show that the thin films have a good crystallinity. Optical properties of the films in the wavelength range of 2.5-12 μm are studied by infrared spectroscopic ellipsometry (IRSE). The optical constants of the BZT thin films are determined by fitting the IRSE data using a classical dispersion formula. As the wavelength increases, the refractive index decreases, while the extinction coefficients increase. The effective static ionic charges are derived, which are smaller than that in a purely ionic material for the BZT thin films.  相似文献   

7.
The deconvolution process of X-ray photoemission spectra for O 1s and Ru 3d, X-ray diffraction and Rutherford backscattering spectrometry reveal that the RuO x films (x = 2.0 – 2.2) deposited at a O2 partial pressure less than 30% show (110)-oriented grains, whereas the RuO x films (x = 2.3 – 2.4) deposited at a 40–50% O2 partial pressure show amorphous and (101)-oriented grains due to the excess O interstitials and RuO3 or RuO4. These differences in the crystal phases of RuO x influence the crystal structure of BaTiO3 deposited on these RuO x bottom electrodes, resulting in a higher dielectric constant and a lower dissipation factor for tetragonal BaTiO3/RuO x (x = 2.1) than amorphous BaTiO3/RuO x (x = 2.4).  相似文献   

8.
This paper presents the chemical bath deposition of zinc selenide (n-ZnSe) nanocrystalline thin films on non-conducting glass substrates, in an aqueous alkaline medium using sodium selenosulphate as Se2− ion source. The X-ray diffraction studies show that the deposited ZnSe material is nanocrystalline with a mixture of hexagonal and cubic phase. The direct optical band gap ‘Eg’ for the as-deposited n-ZnSe films is found to be 3.5 eV. TEM studies show that the ZnSe nanocrystals (NCs) are spherical in shape. Formation of ZnSe has been confirmed with the help of infrared (IR) spectroscopy by observing bands corresponding to the multiphonon absorption. We demonstrate the effect of the deposition temperature and reactant concentration on the structural, optical and electrical properties of ZnSe films.  相似文献   

9.
Several powerful effective medium formulations/approximation (EMA) and associated theories with different origins and concepts have been discussed and utilized here in order to model the experimental refractive index evolutions of ZrO2-SiO2 and Gd2O3-SiO2 composite films with respect to their compositional mixings. Amongst these formulations, the Böttcher's generalized theory has been noticed to have more versatility and can simulate varieties of experimental observations incorporating a form factor parameter to account for the grain structure and morphology to a great extent. The refractive index modeling results of most of the available theories were compared with respect to their functional evolutions and limitations. It was noticed that at higher silica fractions (>20%) in our composite films, the effective experimental refractive index parameters have remained close to the most modeling results and Böttcher's expression has shown to fit the observable parameters very accurately. However, under low silica compositions (<20%) the refractive index values of the composite films depicted different functional evolutions. Such deviations have been attributed to the various morphological, grain structure and band gap supremacies observed in these specific composite films which are not accounted by the effective medium formulations and approximations. These observations are well supported by the atomic force microscopy results.  相似文献   

10.
Z.G. Hu  Y.W. Li  Z.Q. Zhu 《Physics letters. A》2008,372(24):4521-4526
Ferroelectric BaTiO3 nanocrystalline films (BTNFs) with the crystalline sizes of about 30 nm were grown on Pt/Ti/SiO2/Si substrates by a modified sol-gel method. Spectroscopic ellipsometry (SE) was used to characterize the films in the photon energy range of 1.5-5.0 eV with a five-phase layered model (air/surface rough layer/BaTiO3/interface layer/Pt). The optical properties in the transparent and absorption regions have been investigated with the Forouhi-Bloomer dispersion relation. With the aid of the structural and dielectric function models, the microstructure and electronic structure of the BTNFs can be readily obtained. It was found that the refractive index reaches the value of 2.20 in the transparent region. Based on the Sellmeier dispersion analysis, the single-oscillator energy is about 4.7 eV for the BTNFs. The long wavelength refractive index n(0) can be estimated to about 2.00 at zero point. The direct optical band gap energy approaches approximately 4.2 eV and Urbach band tail energy is 262±2 and 268±1 meV respectively with increasing crystalline size. A higher band gap observed can be owing to the known quantum confinement effect in the nanocrystalline formation and different fraction of amorphous and crystalline components. The theoretical analysis based on the effective mass approximation theory is well used to explain these experimental data.  相似文献   

11.
Neutral magnesium atom emission from nanostructured MgO thin films is induced using two-color nanosecond laser excitation. We find that combined vis/UV excitation, for single-color pulse energies below the desorption threshold, induces neutral Mg-atom emission with hyperthermal kinetic energies in the range of 0.1-0.2 eV. The observed metal atom emission is consistent with a mechanism involving rapid electron transfer to three-coordinated Mg surface sites. The two-color Mg-atom signal is significant only for parallel laser polarizations and temporally overlapped laser pulses indicating that intermediate excited states are short-lived compared to the 5 ns laser pulse duration.  相似文献   

12.
BaxSr1-xTiO3 thin films with a compositional gradient of x=0.3 to 1 (in 0.1 mole fraction increments) were fabricated on Pt/Ti/SiO2/Si substrates using a modified sol–gel technique. The graded film crystallised in a perovskite structure and consists of a uniform microstructure with comparatively larger grains. The room-temperature relative dielectric constant (εr) and dielectric loss (cosδ) at 100 kHz were found to be 305 and 0.03 respectively. Dielectric peaks were not observed in the temperature range from -20 °C to 120 °C. The dielectric constant and dielectric loss were almost independent of temperature. Polarisation–electric field measurements at room temperature revealed a saturated but slim hysteresis loop with a remanent polarisation (Pr) of 0.6 μC/cm2 and a coercive field (Ec) of 2.4 kV/mm. The graded film behaves as a stack of BaxSr1-xTiO3 capacitors connected in series and hence the dielectric Curie peaks are removed. Received: 4 October 2001 / Accepted: 17 October 2001 / Published online: 23 January 2002  相似文献   

13.
ZnO thin films are prepared on glass substrates by pulsed filtered cathodic vacuum arc deposition (PFCVAD) at room temperature. Optical parameters such as optical transmittance, reflectance, band tail, dielectric coefficient, refractive index, energy band gap have been studied, discussed and correlated to the changes with film thickness. Kramers-Kronig and dispersion relations were employed to determine the complex refractive index and dielectric constants using reflection data in the ultraviolet-visible-near infrared regions. Films with optical transmittance above 90% in the visible range were prepared at pressure of 6.5 × 10−4 Torr. XRD analysis revealed that all films had a strong ZnO (0 0 2) peak, indicating c-axis orientation. The crystal grain size increased from 14.97 nm to 22.53 nm as the film thickness increased from 139 nm to 427 nm, however no significant change was observed in interplanar distance and crystal lattice constant. Optical energy gap decreased from 3.21 eV to 3.19 eV with increasing the thickness. The transmission in UV region decreased with the increase of film thickness. The refractive index, Urbach tail and real part of complex dielectric constant decreased as the film thickness increased. Oscillator energy of as-deposited films increased from 3.49 eV to 4.78 eV as the thickness increased.  相似文献   

14.
C. Zhu 《Physics letters. A》2007,372(1):81-86
Using Landau-Devonshire (LD)-type phenomenological model, we investigate the phase diagrams and dielectric behaviors of single-domain single-crystal Ba0.6Sr0.4TiO3 films deposited on orthorhombic substrates. An anisotropic strain factor is introduced to quantitatively calculate the effects of anisotropic in-plane misfit strains. Investigation indicates that anisotropic strains play a crucial role on formation of stable ferroelectric phases and dielectric properties. The anisotropic strains induce tetragonal phases which only contain one in-plane spontaneous polarization component. These phases do not exist in BST films of the same composition under isotropic strains. Moreover, permittivity and tunability of films can reach to maximum when the corresponding spontaneous polarization component disappears at the boundaries of structural phase transition.  相似文献   

15.
Fluorescence experiments have been performed to study the interaction of 193-nm laser radiation with dielectric thin films of LaF3, AlF3, and MgF2. Spectral- and time-resolved measurements reveal the presence of cerium in LaF3 and the influence of hydrocarbons in MgF2 and LaF3. Virtually no fluorescence response is observable in the case of AlF3. Supplementary measurements on multilayer stacks confirm the contribution of hydrocarbon and cerium emission in high-reflective UV mirrors upon ArF excimer laser irradiation. Energy density dependent measurements indicate a linear absorption process as the origin of UV laser induced fluorescence in LaF3. Luminescence calculations are applied as a helpful tool in order to account for interference effects that are inherently to be found in the multilayer emission spectra. Received: 21 May 2002 / Accepted: 23 May 2002 / Published online: 10 September 2002 RID="*" ID="*"Corresponding author. Fax: +49-3641/807-601, E-mail: heber@iof.fraunhofer.de  相似文献   

16.
Nanocrystalline nickel ferrite and zinc doped nickel ferrite thin films with general composition Ni1−xZnxFe2O4; x=0.0, 0.2 and 0.5 were fabricated by the spin-deposition technique. Citrate precursor method was adopted to prepare coating solution used for film deposition. This method resulted in single phase, transparent, homogeneous and crack-free nanocrystalline ferrite thin films at annealing temperature as low as 400 °C. The substrates used for film deposition were ITO-coated 7059 glass, fused quartz and Si (1 0 0). The thickness of films was found to be in the range ∼1000–5500 Å. The surface microstructure and morphology investigated by atomic force microscopy (AFM) confirmed the grain size of nickel–zinc ferrite films to be in nanometer range indicating nanocrystalline nature of the films. Dielectric properties such as the real (∈′) and imaginary parts (∈″) of complex permittivity were measured in the X-band microwave frequency region (8–12 GHz) by employing extended cavity perturbation technique. The MH hysteresis measurements on the films annealed at 650 °C revealed narrow hysteresis curves with Hc and Ms varying for different compositions.  相似文献   

17.
Time-resolved luminescence experiments have been set up in order to study the interaction of 193-nm laser radiation with dielectric thin films. At room temperature, Al2O3 coatings show photoluminescence upon ArF excimer laser irradiation, with significant intensity contributions besides the known substrate emission. Time- and energy-resolved measurements indicate the presence of oxygen-defect centers in Al2O3 coatings, which suggests a strong single-photon interaction at 193 nm by F+ and F center absorption. Measurements on highly reflective thin-film stacks, consisting of quarter-wave Al2O3 and SiO2 layers, indicate similar UV excitations, mainly from color centers of Al2O3. Received: 20 February 2002 / Accepted: 11 April 2002 / Published online: 5 July 2002  相似文献   

18.
Ba0.70Sr0.30TiO3 (BST) thin films doped by Co (BSTC) are fabricated by sol-gel method on a Pt/Ti/SiO2/Si substrate. A strong correlation is observed among the microstructure, dielectric, ferroelectric, ferromagnetic properties and Co concentration. The dielectric constant of BST thin films can be tailored from 343 to 119 by manipulating the Co concentration. The dielectric loss of BSTC thin films are still kept below 0.020 and the tunability is above 30% at a dc-applied electric field of 500 kV/cm. With increasing Co doping up to 10 mol%, the coexistence of ferromagnetism and ferroelectrics is found. Suitable dielectric constant, low-dielectric loss, and high tunability of this kind of thin films can be useful for potential tunable applications.  相似文献   

19.
High-k gate dielectric hafnium dioxide films were grown on Si (100) substrate by pulsed laser deposition at room temperature. The as-deposited films were amorphous and that were monoclinic and orthorhombic after annealed at 500°C in air and N2 atmosphere, respectively. After annealed, the accumulation capacitance values increase rapidly and the flat-band voltage shifts from −1.34 V to 0.449 V due to the generation of negative charges via post-annealing. The dielectric constant is in the range of 8–40 depending on the microstructure. The I–V curve indicates that the films possess of a promising low leakage current density of 4.2×10−8 A/cm2 at the applied voltage of −1.5 V.  相似文献   

20.
In this study, effect of indium incorporation on the optical properties is investigated for the spray pyrolyzed onto glass substrates at 275°C substrate temperature undoped and indium doped Cd0.22Zn0.78S thin films. The average optical transmittance of all the films was over 77% in the wavelength range between 450 and 800 nm. The optical band gap energies of the thin films have been investigated by the measurement of the optical absorbance as a function of wavelength. The optical absorption studies reveal that the transitions are direct band gaps of 3.02 and 3.05 eV for undoped and doped indium Cd0.22Zn0.78S thin films, respectively. The Urbach tail parameter and optical constants such as refractive index, extinction coefficient, and dielectric constants were calculated for these films. The dispersion parameters such as single-oscillator energy and dispersive energy were discussed in terms oft he single-oscillator Wemple—DiDomenico model.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号