Investigation of nanocrystals in thin layers of paraffin lubricant on the surface of metals by infrared spectroscopy

It has been shown that when the thickness of a layer of paraffin lubricant on a metal substrate decreases, the crystallites become damaged and the alkane solid solutions become partially separated. Pis’ma Zh. Tekh. Fiz. 24, 40–44 (March 26, 1998)     

Fourier transform infrared spectroscopy characterization of AlN thin films grown on sacrificial silicon oxide layers via metal organic vapor phase epitaxy

Aluminum nitride (AlN) films were grown using metal organic vapor phase epitaxy techniques on Si (111) substrates patterned with silicon oxide (SiO_x) stripes and the vibrational properties of these films were investigated by Fourier transform infrared (FTIR) techniques. The grown films contained a predominantly wurtzite AlN phase. The AlN film on SiO_x was prone to corrosion when subjected to wet etching in buffered hydrofluoric acid solution thereby changing the material properties of the AlN film on SiO_x. The change in the material properties of the AlN films on SiO_x can be gauged from the decrease in the relative integrated areas under the A1 (TO) and E1 (TO) modes of the AlN film. The analysis shows that FTIR is a viable tool for investigating the material properties of AlN thin film structures with lateral dimensions as low as 100 μm.     

Identification of the crystalline-phases in thin pentacene layers by Raman spectroscopy

We investigated the different crystallographic phases in thin pentacene layers by the micro-Raman spectroscopy. For the first time we have determined the presence of orthorhombic, thin film and triclinic bulk phase in thin pentacene layers by the micro-Raman polarization spectroscopy, which were confirmed by XRD measurements.     

Delocalizing strain in a thin metal film on a polymer substrate

Under tension, a freestanding thin metal film usually ruptures at a smaller strain than its bulk counterpart. Often this apparent brittleness does not result from cleavage, but from strain localization, such as necking. By volume conservation, necking causes local elongation. This elongation is much smaller than the film length, and adds little to the overall strain. The film ruptures when the overall strain just exceeds the necking initiation strain, ε_N, which for a weakly hardening film is not far beyond its elastic limit. Now consider a weakly hardening metal film on a steeply hardening polymer substrate. If the metal film is fully bonded to the polymer substrate, the substrate suppresses large local elongation in the film, so that the metal film may deform uniformly far beyond ε_N. If the metal film debonds from the substrate, however, the film becomes freestanding and ruptures at a smaller strain than the fully bonded film; the polymer substrate remains intact. We study strain delocalization in the metal film on the polymer substrate by analyzing incipient and large-amplitude nonuniform deformation, as well as debond-assisted necking. The theoretical considerations call for further experiments to clarify the rupture behavior of the metal-on-polymer laminates.     

Experimental study on buckle evolution of thin inorganic layers on a polymer substrate

In this paper the behavior of a 250 nm and a 350 nm thick Indium tin oxide (ITO) layers deposited on a 200 μm thick high temperature aromatic polyester substrate (Arylite™) and spin coated with a 3 μm silica-acrylate hybrid coating (Hard Coat) is discussed. In-situ optical microscopy of the layered structures under uniaxial compressive strain was used to determine the buckle delamination rate at different applied strains. The effect of applied uniaxial compressive strain and layer thickness on the evolution of buckle width and height was investigated. The biaxial-residual stress, uniaxial compressive stress, poor adhesion at the interface and Poisson’s ratio are believed to be responsible for the formation of telephone-cord buckling.     

The molecular structure ordering and orientation of the metallophthalocyanine CoPc,ZnPc, CuPc,and MgPc thin layers deposited on silicon substrate,as studied by micro-Raman spectroscopy

In this article, we present orientation study of metallophthalocyanine (MPcs) (CoPc, ZnPc, CuPc, and MgPc) thin films deposited on silicon substrate. The MPc’s thin layers were obtained by the quasi-molecular beam evaporation. The micro-Raman scattering spectra of MPc’s thin films were investigated in the spectral range 550–1650 cm⁻¹ using 488 nm excitation wavelength. Raman scattering studies were performed at room temperature before and after annealing process. Annealing process of thin layers was carried out at 200 °C for 6 h. From polarized Raman spectra using surface Raman mapping, the information on polymorphic phase of MPc’s layers has been obtained. The chosen Raman modes A_1g and B_1g are connected with different polymorphic phases of MPc (α and β form) thin layers. Moreover, the obtained results showed the influence of the annealing process on the ordering of the molecular structure. Following the annealing process, it was observed arrangement of the thin layers structure being revealed in Raman spectra. The obtained results indicate that the annealing process has a significant influence on the structure of thin layers being under study.     

The effect of moisture on buckle delamination of thin inorganic layers on a polymer substrate

Moisture-induced buckle delamination of thin inorganic layers on a polymer substrate was studied. Moisture has been found to have a significant effect on the failure mode. Experimentally, an increase in the buckle width, height and the total buckle delamination length with time and humidity was observed. Moreover, a transition from straight to telephone-cord buckle pattern was taken place in a humid environment. Applying only a uniaxial compressive strain on the thin layers did not result in the transition from straight to telephone-cord. For a compliant substrate the transition from straight to telephone-cord buckle occurred at significantly higher ratio of residual strain over critical buckling strain than for a rigid substrate. A simple model for buckling was applied. Using the energy release rate, the interfacial toughness was investigated as a function of relative humidity.     

Development of a planar array infrared reflection spectrograph for reflection-absorption spectroscopy of thin films at metal and water surfaces

Planar array infrared (PA-IR) spectroscopy offers several advantages over Fourier transform infrared (FT-IR) methods, including ultrafast speed (<100 micros temporal resolution) and excellent sensitivity. However, obtaining spectra in the range of 1800 to 1000 cm(-1) of films at the air-water interface remains difficult due to the poor IR reflectivity of water, the extremely low concentration of the thin film on the water subphase, and the interference of water bands. In this study, we report a new planar array infrared reflection spectrograph (PA-IRRS), which has several advantages over conventional approaches. This instrument can record sample and reference spectra simultaneously with an instrumental setup that is the same as that of a single-beam instrument by splitting the incident infrared beam into two sections on a plane mirror (H) or a water trough. With this design, the instrument can accommodate large infrared accessories, such as a water trough, without a loss of infrared beam intensity. Water bands can be subtracted to obtain a high-quality spectrum for poly(L-lactic acid) Langmuir film on the water subphase with a resolution of about 6 cm(-1) in 10.8 s. Hence, this PA-IRRS system has great potential for investigating the time-resolved dynamics of a broad range of Langmuir films, such as cellular membranes or biopolymers, on the water subphase.     

Mechanical spectroscopy of thin layers of PPV polymer on Si substrates

The vibrating reed technique with electro“static” excitation and optical detection has been applied to investigate thin layers of poly-phenylene-vinylene, deposited by spin coating onto microfabricated Si cantilevers, during temperature cycling programs between 90 and 540 K at a rate of 1 K/min. From the vibration frequencies the Young’s modulus of the film can be estimated to be about 10 MPa at room temperature in the precursor phase (if prepared from a solution in toluene), which increases by conversion to the conjugate bonded polymer to about 50 MPa. The temperature dependence of internal friction reveals the processes of γ relaxations (crankshaft motion of side branches in the precursor) and β-relaxation (movements of a few monomer blocks in the polymer chain), as well as peaks indicating the structural transformations during conversion, and possibly a glass transition in the amorphous precursor phase. After conversion only the β-relaxation persists.     

Characterization of ion implantation through thin Ti metal layers on Si

Ion beam mixing of thin Ti films deposited on Si is investigated and its effect during subsequent thermal sintering determined. Both inert (Xe⁺) and dopant (As⁺) ions are used to intermix the metal films and Si substrate. The morphology of the suicide layer formed by this process and the structure of the silicide/Si interface is shown to be independent of the specific ions used for mixing. The structural differences observed are correlated to the electrical resistivity of the films. Transmission electron microscopy (TEM) and Rutherford backscattering spectroscopy (RBS) including ion channeling are used to characterize the films.     

Investigation of the oxidation of a carbon-ceramic composite with infrared reflection spectroscopy

Journal of Materials Science Letters -     

Transient hole formation during the growth of thin metal oxide layers

Using a quinternary variable charge molecular dynamics simulation technique, we have discovered a transient hole formation phenomenon during oxidation of thin aluminum layers on Ni₆₅Co₂₀Fe₁₅ substrates. Holes were found to first develop and expand at the earliest stage of the oxidation. These holes then shrank and finally disappeared as oxidation further proceeded. Thermodynamic analysis of the hole healing indicated that it is accompanied by a significant decrease in system potential energy. This suggests that the effect is largely driven by thermodynamics and is less related to the flux shadowing or kinetically introduced island coalescence. The simulations provide insights for the growth of dielectric tunnel barrier layers with reduced layer thicknesses.     

Investigation of spermatozoa and seminal plasma by fourier transform infrared spectroscopy

Fourier transform infrared (FT-IR) spectra of human spermatozoa and seminal plasma were recorded and analyzed. The procedure that was established for sample preparation enabled acquisition of reproducible spectra. The parameter I(1087)/I(966) for controlling spectra reproducibility was defined. The assignment of bands was carried out using an empirical approach and the origin of the "sperm specific doublet", the bands at 968 cm(-1) and 981 cm(-1), was determined. The principal component regression (PCR) algorithm was used to define the specific spectral regions correlating to characteristics of spermatozoa, such as concentration, straight-line velocity (VSL), and beat cross frequency (BCF). Then, simple spectral parameters, such as band intensities and band ratios, were tested to determine which one best correlates to characteristics of spermatozoa. The region of the amide I band, between 1700 cm(-1) and 1590 cm(-1), was defined as a specific spectral region that correlates to the concentration of spermatozoa. The parameter that gave the linear dependence to the concentration of spermatozoa was the intensity of the amide I band. For VSL, the bands between 1119 cm(-1) and 943 cm(-1) were defined as the specific spectral region. The relative amount of nucleic acids with respect to proteins showed linear dependence on the straight-line velocity of spermatozoa. BCF showed the best correlation to the bands between 3678 cm(-1) and 2749 cm(-1), which largely represent lipids and proteins. These results suggest that FT-IR spectroscopy can serve as an adjunct to conventional histopathology studies.     

在金属薄膜衬底上定向生长碳纳米管

研究和探讨了预处理和温度影响对碳纳米管定向生长机制的作用。利用等离子体增强化学气相沉积(PECVD)的方法,以金属Fe薄膜为催化剂,在单晶硅衬底上定向生长碳纳米管(CNT)。通过给予不同的预处理时间和温度条件,在Fe/Si衬底上沉积出碳纳米管,通过扫描电子显微镜(SEM)进行表征,将不同的条件下生长的碳纳米管进行对比。结果表明,在适当的工艺条件下,可以生长出方向性好,纯度高的碳纳米管。     

Application of thin-film interference coatings in infrared reflection spectroscopy of organic samples in contact with thin metal films

A thin dielectric IR-transparent interlayer is introduced between an IR-transparent medium of incidence and a thin metal film. The interlayer increases the intensity of light on the metal/sample interface at certain wavenumbers. By computations, the reflectivities of the system "calcium fluoride (CaF)-germanium (Ge)-gold (Au) sample" are analyzed as a function of incidence angle and Ge layer thickness. Absorbance spectra with acetonitrile as a sample are recorded for different angles of incidence and polarizations and compared to computations. A characteristic feature of the absorbance spectra is the occurrence of interference fringes distributed between 1000 and 6000?cm(-1), i.e., over the complete mid-IR wavelength range into the near-IR. These fringes could be used in analytical spectroscopy.     

Investigation of aluminium thin layer microstructure on BOPP polymer substrate

In this work, 40 μm biaxially oriented polypropylene (BOPP) polymer substrate is coated in a roll coater system. The single- and double-coated aluminium thin layers are analyzed by XRD, SEM, TEM, AFM and optical light microscopy. The size and density of pinholes are investigated by using TEM, the size of the pinholes are in the range of 0.8–8 μm, it is shown that with increasing sample thickness, the dimension of pinholes decreases. SEM and AFM are applied to study the surface morphology. The results show that the surface roughness of double-coated film is better than the single-coated one and the size of pinholes is smaller. The transmittance through the samples is measured on the UV–Vis range. The results show that double-coated film has significantly low transmittance (almost zero transmittance) in UV–Vis region.     

Investigation of the oxidation of sialons with infrared reflection spectroscopy

Hot-pressedβ-sialons (Si_6-z Al _z O _z N_8-z formed in the Si₃N₄-Al₂O₃-AIN and Si₃N₄-SiO₂-AIN systems have been investigated using infrared reflection spectroscopy (IRRS). Asz increases, the IRRS bands decrease in frequency. The decrease can be explained by the decrease in the force constants of the chemical bondings. IRRS has been applied to the study of the oxidation sialons at 1200 and 1300°C as a function of time. The technique has sensitively detected cristobalite, mullite and glass phases on the oxidized surface. This is considered to be effective for understanding the oxidation kinetics of sialons.     

蓝宝石上GaN基多层膜结构椭偏研究

对InN/GaN/Al2O3和Ga2O3/GaN/Al2O3多层膜结构进行了椭圆偏振光谱研究。所有GaN样品均采用MOCVD工艺在蓝宝石(Al2O3)衬底上生长所得。应用多层介质膜模型,在300～800nm测试波长范围内拟合得到了样品各层厚度和折射率色散关系,并与GaN单层膜色散关系相比较,分析了各层膜之间对自身折射率的影响。研究结果表明,InN和Ga2O3表面均存在一个粗糙层,采用有效介质近似模型可使拟合结果更为准确;相对于GaN单层膜结构,InN薄膜使其下面的GaN层折射率明显增大,这应与界面层态密度有关;而在300～400nm测试范围内,Ga2O3折射率出现反常色散现象,InN消光系数亦产生了一个强的吸收峰,这则可能与GaN层在360nm左右存在的一个强吸收(Eg≈3.4eV)有关。