Antimicrobial properties of diamond-like carbon-silver-platinum nanocomposite thin films

Silver and platinum were incorporated within diamond-like carbon (DLC) thin films using a multicomponent target pulsed laser deposition process. Transmission electron microscopy of the DLC-silver and DLC-platinum composite films reveals that these films self-assemble into particulate nanocomposite structures that possess a high fraction of sp ³-hybridized carbon atoms. Nanoindentation testing of DLC-silver nanocomposite films demonstrates that these films possess hardness and Young’s modulus values of approximately 35 and 350 GPa, respectively. DLC-silver-platinum films demonstrated exceptional antimicrobial properties against Staphylococcus and Pseudomonas aeruginosa bacteria. This paper was presented at the International Symposium on Manufacturing, Properties, and Applications of Nanocrystalline Materials sponsored by the ASM International Nanotechnology Task Force and TMS Powder Materials Committee on October 18–20, 2004 in Columbus, OH.     

Influence of Si content and growth condition on the microstructure and mechanical properties of Ti-Si-N nanocomposite films

Thin films of Ti-Si-N have been prepared by ion beam assisted deposition (IBAD) from two Ti and Si targets. The silicon concentration in the deposited coatings is varied between 0 and 23.7 at.%. The influence of Si content and growth conditions on the microstructure and mechanical properties were investigated using XPS, AFM, XRD and nanoindenter. These nanocomposite coatings exhibit improved mechanical properties in comparison with TiN deposited under the same condition. The hardness measured by nanoindentation reached 42 GPa in Ti-Si-N films containing 11.32 at.% of Si, whereas TiN films only had a value of about 18 GPa. AFM showed that the finest grain size of Ti-Si-N appeared to be 5 nm when Si content was 11.32 at.%. From XPS and XRD results, the microstructures of the high hardness samples were found to consist of nanocrystal TiN grains and amorphous Si₃N₄.     

热处理对TiO2-V2O5纳米复合薄膜结构及性能的影响

以钛酸丁脂、V2O5粉末为前驱体,采用溶胶-凝胶技术制备了TO2-V2O5纳米复合薄膜,并通过椭偏仪、AFM、XRD、TG-DSC和UV-VIS-NIR分光光度计等方法研究热处理对复合薄膜特性的影响.结果表明:随热处理温度的升高,TiO2的结构由非晶到锐钛矿再到金红石相转变,并且金红石相出现和完全转变的温度降低约200℃;晶粒尺寸从5.1 nm逐渐增大227.3 nm;复合薄膜的折射率由1.6增大到2.4,同时薄膜厚度从276 nm降低到187 nm;薄膜在紫外光区的透射率减小,吸收边缘出现红移.     

Physical properties and characterization of Ag doped CdS thin films

Thin films of cadmium sulfide with very well defined preferential orientation and relatively high absorption coefficient were fabricated by thermal evaporation technique. The research is focused to the fabrication and characterization of the compositional data of CdS thin films obtained by using X-ray diffraction, scanning electron microscope along with energy dispersive X-ray spectroscopy. The optical properties were studied by using a UV-VIS-NIR spectrophotometer. The effects of silver-doping by ion exchange process on the properties of as-deposited CdS thin films have been investigated.     

平面应变鼓包实验测量薄膜力学性能的精度分析

采用有限元法系统地研究了平面应变鼓包实验中鼓包尺寸、薄膜初始条件以及材料参数对薄膜变形行为的影响。然后,根据有限元结果,分析平面应变鼓包实验测量薄膜力学性能的精度。结果表明：尽管原有的平面应变鼓包理论模型测量平面应变模量的精度很高,但是依其测量残余应力的精度并不高,尤其是在低残余应力阶段。最后,根据上述情况,提出一种新的分析鼓包实验数据的方法以提高平面应变鼓包技术的精度和可靠性。     

Characterisation and tribological evaluation of nitrogen-containing molybdenum–copper PVD metallic nanocomposite films

This paper reports on the structural, mechanical and tribological properties of molybdenum–copper nanocomposite films ‘doped’ with small amounts of nitrogen, which contain either no nitride phase (i.e. the nitrogen is held in interstitial solid solution, mainly in molybdenum) or small amounts of lower nitrides (i.e. Mo₂N). All films were deposited on Si wafers, AISI M2 high speed steel and AISI 316 stainless steel by reactive sputtering using a hot-filament-enhanced dc unbalanced magnetron system. A systematic approach was adopted to investigate the evolution of metal/metal and ceramic/metal phase combinations with increasing nitrogen content (up to 40 at.% N) in the film. Coating composition and microstructure were determined by cross-sectional TEM, SEM and XPS. XRD was used to identify (where possible) metallic and metal-nitride phases. Mechanical properties such as hardness and elastic modulus were determined by low load Knoop and instrumented Vickers indentation measurements. Reciprocating sliding, micro-abrasion and impact tests were performed to assess tribological performance.

It was found that increasing the nitrogen gas flow rate from 0 to 15 sccm (and therefore nitrogen content in the film from 0 to 24 at.% N), refined significantly the coating microstructure from columnar to a dense and more equiaxed morphology, increasing the hardness whilst maintaining (almost constant) elastic modulus values, close to that of molybdenum metal. Further increases in the nitrogen gas flow rate resulted in films that appeared to contain significant fractions of the Mo₂N ceramic phase. SEM and cross-sectional TEM analyses of the film deposited at a nitrogen flow rate of 20 sccm (containing 36 at.% N) demonstrated a microstructure consisting of 50–100 nm wide columns, which contain small regions of contrast in dark-field images, of the order of 3–5 nm wide. A maximum hardness of 32 GPa and the highest hardness/modulus ratio was however found in the (predominantly metallic) film deposited at a nitrogen gas flow rate of 15 sccm. This film also performed best in both micro-abrasion and impact wear tests; in contrast, the ‘ceramic’ film (deposited at 20 sccm nitrogen flow rate) performed better in reciprocating sliding wear.     

Design of carbide-based nanocomposite thin films by selective alloying

This paper reviews a series of studies on alloying of sputtered TiC coatings with weak carbide-forming metals, Me, such as Al, Fe, Ni, Pt and Cu. Metastable solid solutions with Me on the Ti sites are easily obtained by magnetron sputtering at low temperatures (< 300 °C). First principles density functional theory (DFT) calculations of such carbides show that a driving force exists to remove carbon from the structure as an alternative and kinetically more favourable route compared to Me precipitation. This leads to a situation where additional control of the phase composition is given by annealing: both direct influence during film growth, as well as through subsequent annealing. Thus, alloying of the nanocomposite with weak carbide-forming metals can be used to tune many mechanical, electric and magnetic properties of a carbide-based nanocomposite film.     

Structure, morphology and electrical properties of sputtered Zr-Si-N thin films: From solid solution to nanocomposite

DC reactive magnetron co-sputtering was used for the deposition of Zr-Si-N thin films. Si content (C_Si) was varied by changing the power applied on the Si target, whereas that on Zr target was kept constant. Three series of samples have been deposited at various substrate temperatures: room temperature, 240 °C and 440 °C. The evolution of morphology, crystalline structure, grain size and lattice constant has been investigated by X-ray diffraction analyses. Nanohardness, stress and resistivity measurements provide complementary information, which validate the proposed 3-step model for the film formation of the Zr-Si-N system deposited by reactive magnetron co-sputtering. For low Si content the Si atoms substitute the Zr atoms in the ZrN lattice. Above the solubility limit, a nanocomposite film containing ZrN:Si nanocrystallites and amorphous SiN_y is formed. Further increase of Si content results in a reduction of grain size (D), while the thickness of the SiN_y layer at the crystallite surface remains constant. The increasing amount of the SiN_y amorphous phase in the films is realized by increasing the surface to volume ratio of the crystallites. In this concentration range, the size of the crystallites in the Zr-Si-N films decreases according to the relationship C_Si ∼ 1 / D. With increasing substrate temperature, the solubility limit of Si in ZrN decreases whereas the films' global nitruration (C_N / (C_Si + C_Zr)) increases. The concentration dependence of the electrical resistivity is interpreted in terms of the variation of the SiN_y layer thickness.     

Cu-doping effects on the physical properties of cadmium sulfide thin films

Thin films of CdS were fabricated by close spaced sublimation technique under vacuum of ∼10⁻⁵ mbar at a source temperature of 550 °C for various periods of time. These as-deposited thin films were immersed into Cu (NO₃)₂ solution at 80 ± 5 °C for variety of time to ensure Cu doping. The structural, surface, optical and electrical analyses were completed with the help of X-Ray Diffraction, Scanning Electron Microscope with Energy Dispersive X-Ray, UV-VIS-NIR Spectrophotometer and Hall Measurement System respectively. The transmittance of as-deposited sample is reduced from 80% to 30% with increasing copper immersion time. The mobility increased from 6.67 × 10¹ to 1.15 × 10³ cm²/Vs due to the change in the carrier concentration.     

The effect of Au/Ag ratios on surface composition and optical properties of co-sputtered alloy nanoparticles in Au–Ag:SiO2 thin films

Gold–silver alloy nanoparticles with various Au concentrations in sputtered SiO₂ thin films were synthesized by using RF reactive magnetron co-sputtering and then heat-treated in reducing Ar + H₂ atmosphere at different temperatures. The UV–visible absorption spectra of the bimetallic systems confirmed the formation of alloy nanoparticles. The optical absorption of the Au–Ag alloy nanoparticles exhibited only one plasmon resonance absorption peak located at 450 nm between the absorption bands of pure Au and Ag nanoparticles at 400 and 520 nm, respectively, for the thin films annealed at 800 °C. The maximum absorption wavelength of the surface plasmon band showed a red shift with increasing Au content. XPS results indicated that the alloys were in metallic state, and they had a greater tendency to lose electrons as compared to their corresponding monometallic state. Moreover, the positive and negative shift of the Au(4f) core-level binding energies was observed for low and high Au concentration, respectively. Also a negative shift of the Ag(3d) binding energies was increased by increasing Au concentration. Diffusion of the particles toward the surface by increasing the temperature has also been illustrated by AFM images. Based on AFM observations, we have found that the particle size reduced from 35 to 20 nm by increasing the annealing temperature from 600 to 800 °C, while particle size increased by increasing Au concentration in films. In addition, lateral force microscopy (LFM) analysis showed that the alloy particles were uniformly distributed on the surface.     

衬底温度对Fe-N薄膜结构、形貌及磁性能的影响

采用直流磁控溅射方法,以Ar和N2作为放电气体,在单晶Si(100)衬底上沉积了Fe-N薄膜.采用X射线衍射仪(XRD)、X射线光电子能谱分析仪(XPS)、原子力显微镜(AFM)和超导量子干涉仪(SQUIDS)对所制备的样品进行了结构、成分、形貌和磁性能分析,研究了衬底温度对薄膜的结构、形貌和磁性能的影响.结果表明:衬底温度对Fe-N薄膜的结构有重要的影响,通过控制衬底温度可以获得单相γ′-Fe4N化合物薄膜;γ′-Fe4N具有较高的饱和磁化强度,是非常有应用前景的磁记录介质及磁头功能材料.     

Grain size effect on structural, electrical and mechanical properties of NiTi thin films deposited by magnetron co-sputtering

In the present study NiTi films have been deposited on Si (100) substrates by dc magnetron co-sputtering in the temperature range from room temperature to 923 K. The crystallization, surface morphology and structural features were studied using X-ray diffraction (XRD), atomic force microscope (AFM), field emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM). In situ hot stage atomic force microscope was used to investigate the micro-structural changes during phase transformation in these films. Substrate temperature was found to have a great impact on the structural features and phase transformation behavior of NiTi films. The grain size and the crystallization extent increase with the increase in substrate temperature. Nanoindentation tests of these films were conducted at room temperature. Low hardness and depth recovery ratio was observed in case of the film deposited at substrate temperature of 923 K that could be due to the dominance of martensite phase at room temperature which results in more plastic deformation. The electrical properties of the films were studied using four probe resistivity method. Electrical resistance versus temperature plots show that grain size of NiTi films plays an important role in their electrical properties. NiTi based shape memory alloys exhibit a very interesting martensite to austenite phase transformation as crystal structure changes from monoclinic to cubic upon heating close to room temperature. The characteristics of this transformation are of immense technological importance due to a variety of MEMS applications.     

退火处理对ITO和ITO:Zr薄膜性能的影响

利用磁控溅射在室温条件下沉积ITO薄膜和ITO：Zr薄膜,对比研究在空气中退火处理对ITO和ITO：Zr薄膜性能的影响。结果表明,Zr的掺杂促进了（400）晶面的取向,随着退火温度的升高,薄膜表面颗粒增大,表面粗糙度有所降低。室温下Zr的掺杂显著改善了薄膜的光电性能,随着退火温度的升高,ITO和ITO：Zr薄膜的方阻都表现为先降后升的趋势,ITO：Zr薄膜在较低的退火温度下可见光透过率就可达到80%以上,直接跃迁模型确定的光学禁带宽度Eg呈现了先升后降的变化。ITO：Zr薄膜比ITO薄膜显示了更高的效益指数,揭示了ITO：Zr薄膜具有更好的光电性能。     

Microstructure and mechanical properties of pulsed DC magnetron sputtered nanocomposite Cr-Cu-N thin films

The nanocomposite Cr-Cu-N thin films have been deposited at a substrate temperature of 250 °C by a bipolar asymmetric pulsed DC reactive magnetron sputtering process. Different Cu contents ranging from 0.4 to 14.9 at.% were achieved. The structures of Cr-Cu-N thin films were analyzed by XRD. The surface and cross sectional morphologies of thin films were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The nanoindentation and scratch tests were adopted to evaluate the mechanical and tribological properties of Cr-Cu-N coatings. The influences of Cu content on the structure, mechanical and tribological properties of Cr-Cu-N coatings were explored. It is observed that the columnar structure no longer exists when the Cu content exceeds 10.9 at.%. The stability of CrN phase in the coating is influenced by the Cu content. The scratching coefficient of thin films decreases with increasing Cu content. Sufficient adhesion and tribological properties of Cr-Cu-N coatings are achieved. The maximum average hardness around 20 GPa and scratching coefficient around 0.1 are found in the coatings with around 2.1 to 2.6 at.% Cu in this work.     

The effect of multilayer structure on magnetic properties of FePt thin films

The Fe/Pt multilayer films with different structures were deposited by RF magnetron sputtering on glass substrates, and the L1₀-FePt films were obtained after theas-deposited samples were subjected to vacuum annealing at various temperatures. Results show that the Fe/Pt multilayer structure can effectively reduce the ordering temperature of FePt film, and the in-plane coercivity of [Fe (5.2 nm)/Pt (5.2 nm)]₇ multilayers can reach 161.2 kA/m after annealed at 350 ℃ for 30 min. When Fe and Pt layer thickness is equal, the coercivity of the film is the largest. On the other hand, the different Fe-Pt crystalline phases such as Fe₃Pt and FePt₃ phases are formed after annealing when the thickness ratio of Fe/Pt deviates from 1 after annealing. When Fe and Pt have the same thickness, the thinner single layer gets the lower ordering temperature and the larger coercivity.     

Formation of crystalline Al-Ti-O thin films and their properties

The article reports on the effect of addition of Ti into Al₂O₃ films with Ti on their structure, mechanical properties and oxidation resistance. The main aim of the investigation was to prepare crystalline Al-Ti-O films at substrate temperatures T_s ≤ 500 °C. The films with three different compositions (41, 43 and 67 mol% Al₂O₃) were reactively sputtered from a composed Al/Ti target and their properties were characterized using X-ray diffraction (XRD), X-ray fluorescent spectroscopy (XRF), microhardness testing, and thermogravimetric analysis (TGA). It was found that (1) the addition of Ti stimulates crystallization of Al-Ti-O films at lower substrate temperatures, (2) Al-Ti-O films with a nanocrystalline cubic γ-Al₂O₃ structure, hardness of 25 GPa and zero oxidation in a flowing air up to ∼ 1050 °C can be prepared already at low substrate temperature of 200 °C, and (3) the crystallinity of Al-Ti-O films produced at a given temperature improves with the increasing amount of Ti. The last finding is in a good agreement with the binary phase diagram of the TiO₂-Al₂O₃ system.     

Influence of ultrasonication on the mechanical properties of Cu/Al2O3 nanocomposite thin films during electrocodeposition

To overcome the poor mechanical properties of pure Cu thin films, we performed electrocodeposition to make nanocomposite thin films by incorporating inert Al₂O₃ nanoparticles (50 nm and 300 nm in diameter). In addition, to reduce agglomeration due to their high surface energy, we used ultrasonication during the electrocodeposition. In this paper, we examined the effects of the ultrasonication on the mechanical properties of nanocomposite films with different ultrasonic energy density up to 225 W/cm². Ultrasonication during electrocodeposition efficiently reduced the agglomeration of nanoparticles and reduced the grain size of the Cu matrix. Smaller nanoparticles were more efficiently de-agglomerated by ultrasonication, which resulted in more enhanced mechanical properties in the 50 nm Al₂O₃ nanoparticle-enhanced specimens. Although the addition of nanoparticles in the Cu matrices significantly increased the hardness of the specimens, as observed in nanoindentation tests, we did not observe such an increase in tensile tests. Reducing the grain size by ultrasonication seems to be an important parameter in enhancing the overall mechanical properties of nanocomposites. Ultrasonication provided a significant increase in all mechanical properties, including elastic modulus, yield stress, ultimate tensile stress, and elongation, of all controlled Cu films.     

磁控溅射沉积W-Ti薄膜的结构与性能

采用复合靶磁控共溅射方法在p型(100)单晶硅衬底上制备了不同Ti含量的W-Ti薄膜,并与纯W和纯Ti薄膜作对比。采用XRD、SEM、AFM、显微硬度计和四探针电阻仪对薄膜的结构、成分及性能进行分析表征。结果表明,W-Ti薄膜呈细晶粒多晶结构,Ti含量较低时,W-Ti薄膜呈体心立方相结构,存在W基W(Ti)固溶体。Ti含量较高时,还出现hcp富Ti相。W-Ti薄膜的显微硬度随Ti含量的增加先增后减,而电阻率则随Ti含量的增加而增大。W-Ti薄膜显微硬度均高于纯Ti薄膜,电阻率则高于纯W而低于纯Ti薄膜。     

硬质合金基体金刚石薄膜摩擦学性能研究的进展

硬质合金基体表面沉积金刚石薄膜可以提高其硬度和耐磨性,延长其使用寿命,有效保护和节约钨、钴等稀有金属。作为一种多晶膜,金刚石薄膜的摩擦系数直接影响了其在摩擦学领域的应用。对近年来硬质合金基体表面CVD金刚石薄膜的摩擦磨损性能的研究状况进行了阐述,分析了CVD金刚石薄膜在摩擦实验过程中的摩擦磨损机制,并对金刚石薄膜在摩擦学领域中的应用研究进行了展望。     

Annealing temperature dependence of the optical and structural properties of selenium-rich CdSe thin films

Structural and optical properties of selenium-rich CdSe (SR-CdSe) thin films prepared by thermal evaporation are studied as a function of annealing temperature. X-ray diffraction (XRD) patterns show that the as-prepared films were amorphous, whereas the annealed films are polycrystalline. Analyzing XRD patterns of the annealed films reveal the coexistence of both (hexagonal) Se and (hexagonal) CdSe crystalline phases. Surface roughness of SR-CdSe films is measured using atomic force microscope (AFM). Analyses of the absorption spectra in the wavelength range (200-2500 nm) of SR-CdSe thin films indicates the existence of direct and indirect optical transition mechanisms. The optical band gap (E_g) of as-prepared film is 1.92 and 2.14 eV for the indirect allowed and direct allowed transitions respectively. After annealing, the absorption coefficient and optical band gap were found to decrease, while the values of refractive index (n) and the extinction coefficient (k_ex) increase. The dispersion of the refractive index is described using the Wimple-Di Domenico (WDD) single oscillator model and the dispersion parameters are calculated as a function of annealing temperature. Besides, the high frequency dielectric constant (?_∞) and the ratios of the free carrier concentration to its effective mass (N/m*) are studied as a function of annealing temperature. The results are discussed and correlated in terms of amorphous-crystalline transformations.