AVS2013 Session TF-ThP: Thin Films Poster Session

Nitrogen doped zinc oxide thin films were grown on glass and silicon substrates by reactive magnetron RF sputtering of zinc in a N₂O–Ar atmosphere, post-annealing treatment of samples was made in a nitrogen reactive atmosphere. We report a comparative study of as-grown and post-annealing treatment of N-doped ZnO thin films properties carried out by structural, optical, electrical and spectroscopic techniques. The characterization measurements allow us to confirm the improvement of crystalline quality, a higher incorporation of N, and the apparition of luminescence emission at room temperature and photoresponse in the visible range due to the post-annealing treatment of the samples.

^† : partially funded by CONACyT-Mexico.

In this study, sub-micron structures of hole and line patterns on 4-inch silicon wafer were fabricated by thermal lithography technique using the wavelength of 405 nm laser. Fixed thickness of 80 nm of Quaternary Materials of Ge-Sb-Sn-O (GSSO)thin films were deposited on silicon wafer and glass substrate by magnetron sputter deposition system. The oxygen flow rate ranged from 0 SCCM to 15 SCCM of the sputter deposition process under working pressures of 10 mTorr were studied on the GSSO thin film optical properties of transmittance (T), reflectance (R), absorption (A). Besides, the extinction coefficient (k) of GSSO thin film was controlled between 0.35-1. Furthermore the hole and line structures were made on the GSSO surface with two different laser power ranges of 0.08 mW - 0.3 mW and 0.44mW - 0.88 mW, respectively. The silicon wafer substrate was immersed in Tetramethyl ammonium hydroxide (N(CH₃)₄OH) solution of 2.38 wt% for 30 seconds.

From the experimental results, it can be found that the depth and sidewall shape of the structure were varied with the extinction coefficient (k) of GSSO thin film and the laser power. The diameter of hole and line width of line structures were varied proportional to the extinction coefficient of GSSO thin film when the laser power was fixed at 0.18 mW and 0.66 mW, respectively. When the oxygen flow rate of 0 SCCM, the laser lithography process is unable to produce a pattern on the GSSO thin film surface since it resulted a pure metal thin film. When the oxygen flow rate increases, and the extinction coefficient GSSO thin film is decrease. When the extinction coefficient of GSSO thin film was fixed at 0.4, the V shape was presented in the hole and line structures when the laser powers were less than 0.13 mW and 0.44 mW, respectively. Besides, the structure presented as U shape when the laser power was higher than 0.18 mW for hole structure and 0.66 mW for line structure which the extinction coefficient of GSSO thin film was greater than 0.65. Finally the diameter and line width of two structures can be controlled between 350-700 nm, and the sidewall angle greater than 8 0° can be produced under suitable processing parameters.

In this study, the properties of the ZnO films were studied, which were prepared in different mixing proportion of Argon gases and Oxygen gases. The crystallization behavior of ZnO was analyzed by The XRD spectrum, and crystalline size of ZnO was observed and analyzed by AFM. The effect of the factors, such as annealing temperature, bias voltage of the sample stage and sputtering power, were also studied in the deposition process of ZnO film. Through the studies above, suitable experimental parameters were chosen to prepare the ZnO film, which had a high transmittance and good crystalline properties, making it suitable to prepare ZnO-TFTs.

In a word, the ZnO film was prepared by DC magnetron sputtering, which had a high transmittance and good crystalline properties. The ZnO film with high transmittance is more suitable to prepare transparent thin film transistor. In the next work, ZnO-TFTs will be prepared to study the electronic properties of ZnO film and apply into the flat panel display.

The WO₃C film was deposited on an ITO glass substrate at room temperature by DC reactive magnetron sputtering with W and C target. Effects of carbon concentration on the microstructure, surface morphology and optical properties of WO₃C film were investigated by X-ray diffraction, field emission scanning electron microscopy, atomic force microscopy and spectrometer. X-ray diffraction analysis reveals that all of the as-deposited films are amorphous. The surface roughness of the WO₃C film was increased with increasing carbon content from 0.73 nm to 1.29 nm. The average transmittance of coloured WO₃C film in the visible region (400-700 nm) was decreased with increased carbon content from 0 at.% to 9.35 at%. The optimum average transmittance of about 76.2% and 7.9% during bleaching and coloration states in the visible light region (400-700 nm) with +3V and -3V applied.

The sensing membrane of the pH-ion-sensitive field-effect transistor (pH-ISFET) is a very important element in order to measure continuous monitoring of pH in systems. The Al₂O₃ film among the sensing membrane materials is well-known as a chemically stable dielectric material that has low leakage current, however, it is classified to be poor sensing materials because of their low sensitivity than other sensing membrane materials. The atomic layer deposition (ALD) method meets the good characteristics the Al₂O₃ film, because it is possible for deposition of high density, low impurity level, uniform thickness, and low pinhole density. Also, the pH-sensitivity of the pH-ISFET can be improved by thermal annealing at high-temperatures in O₂ ambient after ALD deposition. In this paper, to apply continuous monitoring, the pH-ISFET with the Al₂O₃ sensing membrane deposited by ALD was fabricated, and its characteristics were investigated.

The n-channel field effect transistor (FET) designed for using the pH-ISFET was fabricated by the CMOS-processing technology. The thermal temperature annealing process of the Al₂O₃ film was carried out using a conventional furnace system in O₂ ambient for 40 min at 500, 600, 700 and 800 ℃. All the measurements of pH-ISFET were carried out in a standard pH solution. The conventional reference of Ag/AgCl and liquid-junction filled with 3 M KCl electrode was used to establish the pH solution potential. The null balance circuit, which maintained constant the drain current and the drain voltage, was used to measure continuous monitoring. In the operation of pH-ISFET sensor, the change of electrochemical potential between the surface of sensing membrane and a reference electrode is generated by the establishment potential with chemical response in the pH solution. In order to ensure the shift of V_T of pH-ISFET with the Al₂O₃ sensing membrane, the I_DS–V_GS curves were measured in pH 4, pH 7 and pH 10 at a constant 600 ℃, these are shown in Fig. 1. From measured results, we confirmed that the V_T of the pH-ISFET was shifted from the pH values which changed the surface potential on the Al₂O₃ sensing membrane. In accordance with experiment results, we measured the shift of the V_T on the pH-ISFETs with Al₂O₃ sensing membrane with respect to the difference of thermal annealing temperatures. Those results are shown in Fig. 2. Through the results of our experiments, we ascertained that the sensitivity of the pH-ISFETs with Al₂O₃ sensing membranes annealed at 500, 600, 700 and, 800 ℃ are about 56.7, 55.2, 50.3, and 33 mV/pH, respectively.

In order to meet the increasing demand for high frequency electronic devices, the physical dimensions of modern MOSFETs have been continuously scaled down to the nanoscale. However, one of the obstacles encountered during the down-scaling process is the tunneling current leakage at gates. SiO₂, traditionally the most commonly used gate dielectric, experiences an appreciable amount of tunneling current leakage when the gate thickness is below 1.0-1.2 nm. Therefore, we propose using alternative high-k dielectrics to replace SiO₂, which can effectively limit the tunneling leakage without losing the current control at gates. Our research is mainly focused on studying Al₂O₃, HfO_2, and Al_xHf_yO_z films deposited onto silicon via Atomic Layer Deposition. The aluminum to h afnium ratio in the oxide is fine-tuned to optimize the electrical and physical properties of the film. We expect Al_xHf_yO_z to have a better interface than HfO₂ and an intermediate band-gap between those of Al₂O₃ and HfO₂. The electrical properties of transistors and devices with gate oxide thicknesses of 5, 10, and 15 nm will be studied. In addition to the C-V and I-V measurements for capacitors and transistors, the films will be characterized by XPS, AFM, and spectroscopic ellipsometry. In addition, we will study the effect of Plasma ALD incorporate with SiN into the high k films. Finally, the effects of various annealing and deposition temperatures at the silicon-oxide interface will be studied using TEM. The discovery of a suitable replacement for SiO₂ would enable the semiconductor industry to push beyond its current limits.

Corrosion behavior is reported for Fe-N films (h = 150 and 300 nm) deposited onto polymer (Fe-PET) and glass (Fe-glass) substrates via DC magnetron sputtering (90 % Ar - 10 % N₂ gas mixture). Polarization curves are obtained in 0.1 M Na₂SO₄ under ongoing Ar bubbling.

Film’s surface is covered with an oxide layer. Fe-PET films show lesser free surface energy in comparison with Fe-glass films (H₂O wetting angle is θ = 77 ± 5° and θ = 87 ± 2°, which gives adhesion energy W_a = 89.1·10^-3 J/m² and W_a = 76.6·10^-3 J/m², respectively). Initial corrosion stage for films on the rigid substrate goes slower than for the polymer substrate: corrosion currents for oxide dissolution and stationary potentials are i_corr = 5·10^-7 A/cm², and E₀ = -0.050 V (vs SHE) for Fe-glass; i_corr = 7·10^-6 А/cm², and E₀ = -0.465 V for Fe-PET.

Film’s thickness influences corrosion rate, but rigidity of substrate does not. Increase in thickness results in increase in corrosion current: i_corr = 1·10^-5 А/cm² for h = 150 nm, and i_corr = 8·10^-5 А/cm² for h = 300 nm. Stationary, passivation and repassivation potentials for Fe-N films after oxide layer removal are E₀ = -0.575 V, E_pass = -0.500 V, and E_repass = +1.350 V. In the case of h = 150 nm, films show localized corrosion. In a passive state, Fe-glass films are more stable then Fe-PET films.

The phenomena observed are probably the results of a mechanical stresses within metal film^[2]. In the case of flexible and plastic substrate these stresses are partially decreased due to sample bend. The rigid substrate produces mechanical stress excess which increases oxide layer thickness and increase initial corrosion durability.

The results reported are of practical interest for thin film devices.

Literature

1. S.S. Maklakov, S.A. Maklakov, I.A. Ryzhikov, K.N. Rozanov, A.V. Osipov, A.S. Naboko, V.A. Amelichev, S.V. Kulikov. The structure and microwave permeability of thin cobalt films. // Nanotechnologies in Russia. 7 (2012) 255-261

2. A.V. Agaponova, I.V. Bykov, S.A. Maklakov, S.S. Maklakov, A.A. Pukhov, I.A. Ryzhikov, M.V. Sedova, E.E. Shalygina, I.T. Yakubov. Visualization of the domain structure of ferromagnetic films using the magnetochemical effect. // Physics of the Solid State. 53 (2011) 1013-1016

We report in this work the structural and optical properties of GaN films grown by the Closed-Space Vapor Transport (CSVT) technique. The samples were deposited on quartz substrates using GaN powder as the starting material source, which were contained inside a semi-hermetic cell made of graphite in a low pressure atmosphere. We present the characterization carried out by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Photoluminescence (PL) measurements. XRD results exhibit the growth of low quality hexagonal GaN, while SEM image shows GaN clusters over the entire substrates surface. Concerning EDS measurements they indicated that non-stoichiometric GaN films with non-intentional carbon (C) impurification were obtained. Finally, PL measurements under UV excitation (He:Cd laser λ=325 nm), present PL emission at room temperature. We observed the presence of different emission bands in the visible region: the yellow (YL) at 2.20 eV and the blue (BL) at 2.7-3.0 eV bands are related to undoped and C-doped GaN, while, the green (GL-2) band at 2.36 eV is related to Ga-rich GaN.

^† : partially funded by CONACyT-SENER, ICyTDF and DGAPA-UNAM PAPIIT.

The ability to pattern substrates is an integral part of many industries, from integrated circuit manufacturing to newspaper printing. To apply features for flexible electronics, techniques such as screen printing, inkjet printing, or shadow masking are available. Alternatively, features can be created by a negative etch if the patterned areas can be sufficiently protected. However, these methods do not offer the ability to use patterning to produce conformally coated 3D structures on complex substrates. Nonwoven fiber mats are an example of a complex substrate, which offers highly tunable properties such as fiber chemistry, diameter and geometry, all of which can be produced in high volumes at very low cost.

In this work, we demonstrate a new method using Atomic Layer Deposition to selectively pattern features on nonwoven fiber mats, allowing for the creation of conformally coated 3D patterns. By compressing the sample between two patterning plates we are able to restrict precursor diffusion in the compressed region, but allow ALD to occur in the exposed portion of the sample, imparting the pattern on the substrate. By stacking multiple layers of substrate in the patterning plates, the 3D pattern that is created can easily be seen by deconstructing the layers or by cutting the sample to view a cross section of the feature. The impact of substrate chemistry (polypropylene, nylon, cotton) and structure (woven vs. nonwoven) as well as fiber diameter (microfibers vs. nanofibers) is examined. In addition the impact of deposition conditions (temperature, precursor exposure) and coating chemistry (Al₂O₃ and ZnO) is investigated. This technique will enable new applications for ALD coatings on flexible substrates; applications in gas and liquid sensors as well as flexible electronics will be discussed.

Cu interconnects in modern integrated circuits are fabricated using an electroplating process, which requires an ultrathin, conformal, and continuous Cu seed layer. The resulting interconnect performance depends significantly on the quality of this seed layer. Atomic layer deposition (ALD) is a thin film growth technique, which is widely used to deposit highly conformal, high-purity films with digital control over the thickness. This technique has been successfully implemented to deposit a variety of metals. To enable new deposition chemistries, and to achieve better control over existing ones, it is important to understand the surface reaction processes that occur during film growth. In situ infrared spectroscopy has been shown to be an excellent technique to study surface reactions in an ALD processing environment. However, due to free electron absorption in metals, traditional infrared techniques based on transmission and internal reflection cannot be used to study metal ALD processes beyond the very initial nucleation stage. In this study, we have designed and implemented an in situ reflection-absorption infrared spectroscopy (RAIRS) setup to study the surface reactions during the deposition of Cu from Cu(hfac)₂ and a remote H₂ plasma at a substrate temperature of 80 °C. We specifically report on the surface reactive sites, and the mechanism for Cu(hfac)₂ chemisorption on an oxide (Al₂O₃) surface. Unlike previous studies, we propose a detailed surface reaction mechanism, which does not require the presence of hydroxyl groups on the oxide surface. Lastly, using RAIRS, we also report results with the use of reducing agents other than atomic H, and report on their efficacy.

Most applications of Mo/Si bilayers mirrors in extreme-ultraviolet lithography (EUVL) require a high normal-incidence reflectivity. This work represents our effort to design and prepare the Mo/Si multilayer film with 4 nm bandwidth at 13.5 nm wavelength. The Mo/Si multilayer film was deposited on a Si substrate at room temperature by RF magnetron sputtering with Ar gas. The optimum simulation reveals that normal-incidence average reflectivity of Mo/Si multilayer film with 4 nm bandwidth at 13.5 nm was 14%. Effects of RF power and working pressure on the microstructure, surface morphology and EUV reflectivity of Mo/Si multilayer film were investigated by X-ray diffraction, atomic force microscopy and high resolution transmission electron microscopy (HRTEM). It was found that the surface roughness of Mo/Si multilayer film was significantly improved under 0.2 nm at low RF power and work pressure. In addition, HRTEM lattice fringe revealed that Mo film was polycrystalline and Si film was amorphous. The resulting EUV bandwidth of this Mo/Si multilayer film is 4 nm (λ=13.5 nm, α=15^o ).

We demonstrate the growth of atomically thin (mono to few layer) alloys of Molybdenum Sulphoselenide films with the use of organic sulfur and organic selenium precursors. Changing the ratio of these precursors allows us to tune the value of the band gap continuously between 1.87 eV and 1.54 eV, the band gaps of MoS₂ and MoSe₂, respectively. Our growth technique yields mm scale films on SiO₂/Si (300 nm oxide layer) substrates. The films are characterized with Raman spectroscopy, X-ray photoelectron spectroscopy, photoluminescence measurements, and atomic force microscopy

Laser interferometer gravitational wave telescopes need baffles to avoid stray light in UHV. The surface of baffles should be treated with anti-reflection coatings without scattering light and increasing outgassing. Diamond-like Carbon (DLC) films are suitable for this aim. The reflectivity of DLC films on SS304 was less than 1% at minimum for 1064nm in wavelength. We could optimize the thickness of the film so that the reflectivity can be less than 20% for any polarization, wide incident angle, and large inhomogeneity of thickness.

Coating in the lumen surface of long and thin tubes has been highly desired yet challenging. In this work, generation of stable plasmas in a long thin tube and the use of such plasmas to perform plasma polymerization in the lumen surface of the tube are presented. By inserting a specially designed long thin electrode into the tube, stable Ar or He discharges can be sustained in tubes with the inner diameter down to 0.26 mm and the length up to 1 m under atmospheric pressure using an AC power source. This system is then used to perform plasma polymerization in the lumen surface of a tube 1 mm in inner diameter. When allylamine is used as the precursor, carried by Ar gas flow, films containing NH_x can be obtained through plasma polymerization. The film composition is examined by ATR-FTIR. The spectra show the absorption at 3274 cm^-1, which is attributed to NH_x, and the absorption at 1658cm^-1, contributed by C=N, C=C, or N-H. Further analyses using SEM, XPS, and AFM show that smooth film with NH_x–bonded surface can be obtained. Such an approach offers a promising approach in various fields such as biomaterial application.

We will present our work demonstrating polymer deposition onto ionic liquid (IL) substrates. ILs have recently attracted significant interest as an environmentally-friendly alternative to traditional volatile organic solvents because ILs are non-volatile, non-flammable, and can be easily recycled. The low volatility of ILs allows for their use in vacuum processing. The immobilization and encapsulation of ILs is important to implementing ILs in commercial processes to bypass issues caused by their high viscosity. We will demonstrate the encapsulation of IL droplets in polymer shells and the integration of ILs into layered polymer films. Our encapsulation method uses a liquid marble technique to deposit a continuous polymer shell on the entire area of IL droplets. Polymer shells composed of 1H,1H,2H,2H-perfluorodecyl acrylate crosslinked with ethylene glycol diacrylate (P(PFDA-co-EGDA)) were found to be stronger than the respective homopolymers. We also studied the immobilization of IL in layered polymer films made by sequential and simultaneous depositions of soluble and insoluble monomers. We found that the polymerization of soluble monomers within the bulk IL leads to the integration of the IL into the polymer films and that the order in which the monomers are introduced into our polymerization process significantly affects the structure of the layered films.

Recently the promise of thin film solar cells has begun to be realized on a commercial scale with the introduction of CdTe and CuInGaSe modules in the market place. Although these materials yield cost-effective modules from a dollar/watt aspect they present environmental and possibly long term availability issues. In view of this a great deal of interest is being focused on environmentally safe earth abundant materials including iron sulfide (FeS₂) in the pyrite phase, and tin sulfide (SnS). While promising, iron sulfide is presenting serious material science challenges, while work on SnS is just beginning. In addition the band gaps of these materials are less than the optimal value of 1.36 eV. Another excellent candidate for an earth abundant absorber material is WSe₂ which can be directly grown as a p-type semiconductor with a band gap near 1.4 eV. In view of this we have evaluated the performance of WSe₂ in photovoltaic devices by means of numerical modeling. The model is based on thin film material properties obtained from the literature as well as those measured in our laboratory. These results will be compared to those obtained for FeS₂ where it will be shown that WSe₂ has a significantly higher potential for yielding devices with efficiencies in the 20% range.

Ag thin films with excellent physical properties have been used as electrode, optical reflector, and so on. It is necessary to prevent degradation of the Ag films in air or humid atmosphere. We pay attention to sub-nanometer thick layer of 3-mercapto propyltrimethoxysilane (MPTMS), as a protective coating. If the MPTMS monolayer is formed at the surface of Ag thin films, a strong bond between them may bring an effective passivation of the Ag films.

Ag thin films (10nm) were deposited on clean glass substrates by vacuum evaporation. Then monolayer of MPTMS was formed over the Ag thin films by solution method. The samples were kept in a constant temperature and humidity chamber (40 degree celsius and 80 RH%) for a week. The electrical resistance, surface morphology, optical transmittance were measured before and after the test. Ag film without the monolayer was also examined for comparison.

The surface roughness (rms) of the Ag film modified with the monolayer was increased from 2.1 nm to 3.8 nm after the test. However, that of Ag film without the monolayer drastically increased from 3.7 nm to 12.4 nm. As a result, passivation effect of the MPTMS monolayer for Ag films was confirmed. By the measurement of electrical resistivity, it was found that increase in the resistivity after the test was very much suppressed in the Ag film with MPTMS monolayer. In addition, optical transmittance measurement showed that spectrum of Ag films with the monolayer did not change after the test. These results accord with film morphology change. Consequently, we found modification of Ag films with MPTMS monolayer can improve durability of the Ag films.

Recently, the flexible display applications have attracted attention as the next generation industry and related researches and mass production compatible products grew fast during the past few years. Until now, most of these systems have several disadvantages due to the stacked structure. Most of the processes for flexible display applications still use the high aspect ratio of the stacked on the flexible substrates. The high aspect ratio will affects reliability concerns under bending states. In order to solve these problems, a new concept has been studied. Among them, a concept of embedded structure inside the flexible substrate without changing the substrate’s thickness was proposed with laser ablation and screen printing. However, the surface conditions of the flexible substrate cannot be controlled using laser ablation. In order to solve these problems, the surface treatment process was proposed with optimized conditions for the substrate preparation. This work focuses on the surface properties of etched PAR substrate plasma treatment with a goal of low fragmentation, smooth surface roughness, and high overall transmittance with different process parameters.

New materials and new device architectures have created an increasing need for Atomic Layer Deposition (ALD) of nano-scale conformal films to be incorporated into the manufacturing process flow. The conformality of ALD films is required to form some of the functional layers in today’s leading-edge planar IC devices, and in three-dimensional (3D) multi-gate CMOS devices such as “finFETs.” However, especially at the beginning of an R&D evaluation, ALD research involves expensive and exotic precursors that may only be available in small quantities. Therefore, there is a need to be as efficient as possible when exploring the potential use of a new ALD precursor for commercial manufacturing.

This drive towards efficiency often leads research in the direction of small volume, “coupon”-based reactors to attempt initial learning. Unfortunately, often results don’t translate from small reactors to full 300mm diameter silicon wafers, and this problem is only expected to become worse as the industry transitions to 450mm diameter wafers. In addition, performing experimentation at 300mm allows for integration of ALD films with other state-of-the-art processes to generate the stacks of materials necessary to extract the key electrical data necessary to evaluate device performance. Therefore, there is a pressing need for a more efficient approach that allows ALD R&D to occur on full 300mm diameter wafers.

One such approach is to use a high productivity combinatorial (HPC™) platform—such as that developed by Intermolecular, Inc.—to dramatically accelerate R&D of integrated ALD films by 10-100x relative to traditional methods. Combinatorial ALD can be integrated with combinatorial processes for wet-etching/cleaning and physical vapor deposition/chemical vapor deposition (PVD/CVD) to engineer interfaces and multilayer stacks for optimal device performance.

In one Collaborative Development Program with an Intermolecular customer, the initial design-of-experiments to integrate an ALD film with novel substrates, overlayers, and annealing resulted in over 3500 required tests to completely explore the potential solutions-space. It was estimated that a conventional R&D approach would have taken 2 years while using the HPC platform allowed the team to identify a combination of materials with the desired properties in just 7 months with a 75% reduction in raw materials expenses for ALD precursors and wafers.

Hydrogen cracking of steels is a major concern in steel processing and service, and occurs in several applications, such as cracking of rolled steel products, cold cracking of welds, and as a result of corrosion in H₂S environments.

Low-permeation thin films can be used as hydrogen permeation barriers. When coated on stainless steel they can reduce the rate of hydrogen transport. And they might be useful for sterling engines, tritium containment, or components of hydrogen fuel cells.

The hydrogen permeation behavior of BN-coated SUS316L stainless steel was investigated. The c-BN (cubic boron nitride) coating, deposited by magnetically enhanced plasma ion plating, was effective to reduce the rate of hydrogen permeation through stainless steel. The c-BN coating is also known as high-performance coating for cutting tools at high temperature.

This can be used for high-temperature and wear-resistant applications as hydrogen permeation barriers.

Much attention has recently been given to the conclusion of Pendry [1] that a thin film of material with a negative refractive index can achieve imaging of unlimited resolution. Pendry’s analysis was stimulated by Veselago’s work [2], which showed that negative-index material could be used to focus propagating waves, where resolution is necessarily wavelength-limited. In principle, both are a consequence of the standard boundary conditions of an interface between a medium with positive magnetic and dielectric material constants μ and ε, respectively, and a medium with negative values of these parameters. Here, we examine the situation considering both Maxwell’s Equations and the theory of complex variables, taking into account ranges of phase of μ and ε allowed by causality. We find that “negative index” can be defined simply as arg(με) > π (Pi), replacing equivalent but awkward definitions in the literature. We show that in such materials energy flow and attenuation of propagating waves are rigorously in the forward direction for all values of μ and ε consistent with causality, even if the phase velocity is reversed. Veselago’s conclusion is consistent with the Green-function solution of the Helmholtz Equation for a point source, but only for a coherent source under steady-state conditions. For a flash source it fails the Abbé criterion, since rays following different paths arrive at different times. Pendry’s solution is not appropriate for point sources, but requires excitation by large-area evanescent waves. These can be generated for example in the Otto or Kretschmann configurations, which have been used extensively to investigate plasmons at metal interfaces. They can also be high spatial Fourier coefficients of local fields resulting from screening charge at boundaries in nanoscopically inhomogeneous overlayers driven by longer-wavelength illumination, as described by effective-medium theory. For sufficiently thin films Pendry’s “imaging” process reduces to the appearance of a resonant plasmon on the opposite side of the film, as described by Raether [3], and hence is not imaging in the usual sense of the word. The attenuation of the resonant plasmon on the opposite side appears as amplification from the source side. All data so far claiming subwavelength resolution are consistent with this interpretation. In short, the perfect lens does not, and cannot, exist.

[1] V. G. Veselago, Soviet Physics Uspekhi 10, 509 (1968).

[2] J. B. Pendry, Physical Review Letters 85, 3966 (2000).

The x-ray diffraction techniques is commonly used to study the microstructure in crystalline materials; in the case of thin films and coatings (especially with thickness lower than 2 micrometers) it is difficult to avoid the influence of the substrate when the Bragg-Brentano mode is used since the signal from the diffracted peaks of the substrate can be overlapped with the diffraction peaks of the films, and the effect is more severe in the case of polycrystalline substrates. The grazing incidence x-ray diffraction technique (GIXRD) can solve that problem, bringing information of the structure of the film without signal from the substrate. However, it is important to understand that grain size and preferred orientations cannot be estimated from the diffraction patterns obtained in the GIXRD mode. In order to show the validity of this statement, metal nitride coatings were analyzed using both GIXRD and the Brag-Brentano modes, as well as the more recent In-Plane mode (detection of the diffraction from the perpendicular planes to the surface) and pole figures. The results indicated that GIXRD is not suitable to study the preferential orientation of coatings and thin films due to possible gradients in the structure of the coatings which lead to wrong results that do not correspond to the real structure of the material. Similarly, for the grain size that is a function of the peak width, it was found that the value obtained from the GIXRD is not close to the values obtained using the Bragg-Brentano mode, since the resolution of the peaks is poor and the instrumental broadening is too wide in the GIXRD geometry, to determine small grain sizes.

Using the analysis of the results, it was concluded that GIXRD is a good technique that can provide information about the crystalline phases in thin film and coating without influence of the substrate, but need to be complementary with the other XRD techniques in order to study the texture and/or preferential orientation.