Mg/Nb复合薄膜的结构调控及其对脱氢温度的影响

利用磁控溅射法制备了两组Mg/Nb复合薄膜,研究了不同Nb层厚度和不同基底温度对Mg/Nb复合薄膜脱氢温度的影响。结果表明,当Nb层厚度为1nm和2nm时,其催化效果相对最好,可使Mg/Nb复合薄膜的脱氢温度分别降至110℃和122℃。当基底温度为125℃时对脱氢性能的改善效果最佳,可使Mg(100nm)/Nb(1nm)复合薄膜的脱氢温度降至100℃。同时,讨论了Nb层厚度和基底温度对Mg/Nb复合薄膜脱氢温度的影响机制。     

Zr/Nb薄膜材料的制备及界面结构研究

通过直流磁控溅射法在单晶Si(100)基底上制备了Zr/Nb/Si薄膜材料。X射线衍射(XRD)研究表明Zr薄膜以多晶形式存在,而Nb薄膜则形成了(110)晶面择优生长。薄膜中Zr和Nb晶粒大小分别为14,6 nm。扫描电镜研究表明形成的薄膜表面平整光滑,没有微裂纹存在。扫描俄歇电子能谱及X射线光电子能谱的研究表明,Zr/Nb/Si薄膜样品具有清晰的界面结构。在薄膜表面形成了致密的氧化层物种,而在膜层内部少量氧则以吸附态形式存在。     

Substitution of Nb doping on the structural, microstructural and electrical properties in PZT films

Undoped and niobium (Nb) doped Pb_1−y(Zr_0.54Ti_0.46)_1−yNb_yO₃ have been deposited by sputtering on Pt metallized silicon substrates. The niobium concentration, y, was varied from 1 to 7 at.% by 1 at.%. The Zr/Ti ratio was fixed to 54/46 corresponding to the Morphotropic Phase Boundary. Structural, microstructural, and electrical properties were evaluated depending on Nb content. The films (doped and undoped) present a (1 1 1)-preferred orientation. The Nb doping induces an increase of the grain size and as it was observed in bulk materials the dielectric constant (ε_r) and the piezoelectric coefficients (e₃₁ and d₃₃) reach their maximum for low Nb concentration (2 at.%). The remnant and the maximum polarizations increase as the coercive field decreased slightly with the Nb concentration. The internal electric field increases with Nb content; as a result, the ‘self-polarization’ of the films (polarization measured without poling treatment) is enhanced with niobium substitution. In term of fatigue behavior, it was found that switching endurance characteristics are maximum for low Nb doping level.     

Preparation and characterization of sputtered Cu films containing insoluble Nb

Copper films containing various amounts of insoluble Nb (up to 24.7 at.%) were prepared by r.f. magnetron sputtering. The crystallography and microstructure of the films were investigated for as-deposited and annealed Cu(Nb) thin films. Cu(Nb) thin films are found to consist of non-equilibrium supersaturated solid solution of Nb in Cu with a nanocrystalline microstructure. X-ray diffraction and scanning electron microscope analyses revealed a reduction in the grain sizes of the films with increasing Nb content in the films leading to a grain refinement. The electrical resistivity of as-deposited and annealed Cu(Nb) thin films is found to be low for an Nb content 2.7 at.%. Significant drops in the resistivity were observed for the high Nb contents after annealing at 530 °C which may be due to grain growth and formation of Nb-bearing phase in the film. Microhardness of the films was found to increase with the Nb concentration due to the combined effects of grain refinement and the solute strengthening of Nb.     

Structure and magnetic properties of sputtered FePtM (M = Ti,Nb) thin films

FePt thin films doped with various Ti and Nb concentrations ranging from 2.9 to 9.1 at.% were prepared by r.f. magnetron sputtering. The structural and magnetic properties of Ti- and Nb-doped FePt thin films were investigated. Structural studies revealed that the long range ordering in FePt thin films depends on the doping concentration and annealing temperature of FePt thin films. The addition of Ti and Nb is found to enhance the grain refining in FePt thin films. The effects of doping concentration on the magnetic properties of FePt thin films were studied and discussed.     

Effect of oxygen on the dielectric and energy storage performances of lead-free Bi2Mg2/3Nb4/3O7 thin films prepared by magnetron sputtering

Journal of Materials Science: Materials in Electronics - Bi2Mg2/3Nb4/3O7 (BMN) thin films are prepared on Pt–Si substrates by magnetron sputtering, the influence of oxygen on dielectric and...     

Nb3Si films with zero resistance Tc at 11.9 K fabricated by sputtering Nb on Si substrates

Dendritic textured Nb₃Si thin films, deposited by sputtering pure niobium onto silicon substrates, exhibit a rather high zero-resistance critical temperature, T_c. X-ray and TEM measurements reveal the films to be polycrystalline with the A15 phase. The resistance begins to drop sharply at a temperature of 13.3 K and down to zero at 11.9 K without residual resistivity.     

Formation of porous niobium films by oblique angle deposition: Influence of substrate morphology

The present work demonstrates the formation of porous niobium films with separated columnar structures by oblique angle magnetron sputtering for capacitor application. The niobium films deposited on textured aluminium substrates, which had concave cell structures with the cell sizes ranging from 125 nm to 550 nm, consist of isolated columns of niobium with wider gaps between columns developing on the substrates with larger cell sizes. The surface areas of the deposited films, evaluated by the capacitance of the anodic films formed at several voltages, increased with an increase in the cell size of substrate. The surface area decreases with an increase in the formation potential of anodic films from 2 V to 10 V vs Ag/AgCl, because the gaps are filled with anodic oxide as a consequence of the large Pilling-Bedworth ratio of 2.6 for the Nb/Nb₂O₅ system. The reduction of the surface area is suppressed when the substrate with larger cell size is used, due to the formation of niobium columns with wider gaps, which are not filled with anodic oxide. The high surface area even at higher formation voltages of the anodic films is a requisite for capacitor application.     

Growth of niobium oxide films on single-crystal silicon

200-nm-thick niobium films grown on single-crystal silicon wafers by magnetron sputtering have been oxidized by annealing in flowing oxygen. X-ray diffraction examination revealed the metal-like phase Nb₆O in the as-deposited films. Annealing in flowing oxygen for 1 h led to the formation of tetragonal NbO₂ at 570 K and hexagonal Nb₂O₅ at temperatures above 770 K. The grain size and surface roughness of the films were evaluated using atomic force microscopy.     

Silicide formation and phase separation from Cu/Nb and Nb/Cu bilayers on silicon

Electron beam evaporation was used to produce Nb/Cu and Cu/Nb bilayers on silicon. The phase sequence and morphology were investigated as a function of annealing temperature in the temperature range between 200 °C and 800 °C, using Auger electron spectroscopy, Rutherford backscattering spectrometry, X-ray diffraction, and transmission electron microscopy. Independently of the sequence of deposition, the phases Nb₃Si and Nb₅Si₃ are the two first niobium phases to be formed as a very thin layer at the Nb---Si interface. However, there is evidence that the reaction between niobium and silicon depends strongly on the presence of copper at the Nb---Si interface. The unusual coexistence of Nb₅Si₃, NbSi₂ and niobium phases was also observed. The formation of the ternary phase Nb₅Cu₄Si₄ was detected after annealing Cu/Nb at 700 °C and Nb/Cu at 800 °C. In the latter case the NbSi₂ and Cu₃Si+Cu₄Si phases were formed through a layered growth process.     

Nb–Al–N thin films: Structural transition from nanocrystalline solid solution nc-(Nb,Al)N into nanocomposite nc-(Nb,Al)N/a–AlN

Structures and mechanical properties of thin films of the Nb–Al–N system produced by magnetron sputtering of targets from niobium and aluminum in the Ar–N₂ atmosphere have been studied. It has been shown that as the aluminum concentration increases, the structure of a thin film transforms from the nanocrystalline into the nanocomposite one, which consists of nanocrystallites of solid solutions in a matrix of amorphous aluminum nitride. Hardness, elastic modulus, and yield strength of Nb–Al–N thin films have been studied by nanoindentation in the mode of continuous control of the contact stiffness. It has been found that the transition of the structures of Nb–Al–N thin films from the nanocrystalline to the nanocomposite structures results in an increase of hardness and decrease of elastic modulus due to the formation of a thin amorphous interlayer between grains of nanocrystallites. A high hardness to elastic modulus ratio of Nb–Al–N nanocomposite thin films indicates that the films are a promising material for wear-resistant coatings.     

Atomic scale microstructures of high-k HfSiO thin films fabricated by magnetron sputtering

High-k hafnium-silicate films were deposited by RF magnetron sputtering approach on silicon wafer. The microstructure has been investigated using the combination of transmission electron microscopy and atom probe tomography. It was evidenced that the elaborated HfSiO thin films subsequently annealed at 950 °C during 15 min leads to a complex phase separated nanostructure where silica, hafnia and silicon nanoclusters coexist. The formation of silicon nanoclusters in hafnia-based host was never reported before. The results demonstrate the capability of RF magnetron sputtering to pave the way for realization of nanomemory devices based on silicon clusters embedded in high-k matrix.     

Preparation of polycrystalline films of NbO2 BY rf sputtering

Niobate films have been prepared by the radiofrequency sputtering of NbO₂ targets. Polycrystalline films have been deposited onto silicon substrates maintained at temperatures exceeding 620°C during preparation. Characterisation by X-ray diffraction indicates that the argon environment during sputtering must be doped with approximately 500 to 1000 ppm of hydrogen for the growth of films of niobium dioxide.     

用AFM研究硅基上沉积铜膜生长过程

室温下,利用磁控溅射在P型Si(111)衬底上沉积了铜(Cu)膜.用原子力显微镜(AFM)对不同沉积时间制备的Cu膜形貌进行了观测,研究了磁控溅射沉积Cu膜时膜在硅衬底上成核和生长方式.Cu膜在Si衬底生长时,Cu的临界核以Volmer-Weber模式生长.溅射时,核长大增高为岛状,岛与岛相互连接构成岛的通道,最后形成连续膜.随着沉积的进行,Cu膜表面粗糙度由于晶粒凝聚和合并而增大.当形成连续致密的、具有一定晶向的Cu膜时,粗糙度反而减小.     

X-ray photoelectron spectroscopy study of the initial growth of transition metal nanoscale films on (100) Si substrates

The initial growth stages of materials non-active to a substrate has been extensively studied for decades, whereas there had been fewer studies on the initial growth of active metals on silicon substrate, despite its technological importance. In this paper the very early growth stages of transition metal (Ti, V and Nb) films deposited by rf sputtering on unheated (100) Si substrate were studied by in situ X-ray photoelectron spectroscopy. The following sequence of the phase composition and the growth mechanism changes during deposition process was revealed. Initially in a submonolayer regime, small 3D TiO₂ islands are formed via reduction of a native silicon oxide layer on a substrate followed by formation of a TiO phase between TiO₂ islands and on their top. After deposition of ca. 2 monolayers a metallic Ti phase appears and later only the metal Ti film grows. The same growth behavior takes place at Nb and V deposition with a difference that in the case of Nb the above changes occur at earlier stages what can be explained by the highest niobium activity to the reduction of silicon oxide in the row V, Nb, Ti.     

超导Nb膜表面减反膜技术研究

针对单光子探测芯片中超导Nb膜减反的问题,研究了磁控溅射Nb膜折射率光谱特性随Nb膜厚度变化的规律,同时研究了化学气相沉积法制备的SiO₂和SiN_x介质膜的折射率光谱特性。为降低超导Nb膜对633 nm光的反射比,在Nb膜表面设计和制备了SiO₂和SiN_x减反膜。测试结果表明:SiO₂和SiN_x使反射比明显减小,计算结果验证了这一趋势。     

Preparation and characterization of biocompatible Nb-C coatings

Nb-C composite films, obtained by DC magnetron sputtering method, were investigated as possible candidates for the protective layers used in medical implants. Coatings of different carbon/niobium ratios were prepared and analyzed for elemental and phase composition, crystallographic structure, texture, corrosion behavior, and cell viability. The coating with the highest C/Nb ratio (≈ 1.9) was found to have a nanocomposite structure, in which NbC nanocrystalline phase coexists with an amorphous a-C one. The coated samples exhibited an improved corrosion resistance as compared with the Ti alloy. Cell viability measurements proved that human osteosarcoma cells are adherent to the coating surfaces, the highest viability being found for the film with the highest carbon content.     

Thermal Oxidation of Thin Cu–Ti Films

Thin Cu–Ti films are grown on single-crystal silicon substrates by magnetron sputtering, and their oxidation is studied between 420 and 670 K. A technique is proposed for producing Cu–Ti films of controlled composition using a composite target. The phase composition of the films oxidized in oxygen at atmospheric pressure is determined, and their microstructure is studied by scanning electron microscopy. The films are found to contain the intermetallic compounds Cu₃Ti and CuTi₂, which form during both magnetron sputtering and subsequent oxidation.     

Reactive pulsed-DC sputtered Nb-doped VO2 coatings for smart thermochromic windows with active solar control

Thermochromic VO2 thin films have successfully been grown on SiO2-coated float glass by reactive pulsed-DC magnetron sputtering. Different Nb doping amounts were introduced in the VO2 solid solution during the film growing which resulted in films with distinct semiconducting-metal phase transition temperatures. Pure VO2 showed improved thermochromic behavior as compared with VO2 films prepared by conventional DC sputtering. The transition temperatures were linearly decreased from 59 down to 34 degrees C with the increase in Nb content. However, the luminous transmittance and the infrared modulation efficiency were markedly affected. The surface morphology of the films was examined by scanning electron microscopy (SEM) and showed a tendency for grain sized reduction due to Nb addition. Moreover, the films were found to be very dense with no columnar microstructure. Structural analyses carried out by X-ray diffractometry (XRD) revealed that Nb introduces significant amount of defects in the crystal lattice which clearly degrade the optical properties.     

Large area ZnO:Al films with tailored light scattering properties for photovoltaic applications

Aluminum-doped zinc oxide films on glass are promising substrates for use in thin film solar cells based on amorphous and amorphous/microcrystalline silicon absorber material. The films can be produced by magnetron sputtering on large scale at relative low cost. Especially reactive sputtering of metallic Zn/Al compound targets is a cheap way to produce films at high deposition rate. One drawback of amorphous silicon is the low absorption in the near infrared spectral range. Wet chemical etching has been used to produce a rough TCO surface that enables light trapping in the absorber. The etching behaviour of ZnO:Al films can be tuned by changing oxygen partial pressure during deposition. The etching behaviour is compared to ZnO structure and discussed regarding the performance of solar cells deposited onto the etched films.