ICMCTF2013 Session FP: Syposium F Poster Session

There is currently great interest to design and fabricate novel flexible devices for solar cell, solid-state lighting, biomedical and energy harvesting applications. Such devices require the use of electrode components. Desired electrodes must exhibit structural integrity, low electrical resistivity and, in most cases, high optical transparency in the visible range.

Despite growing efforts to replace them, transparent conducting oxides layers deposited on polymer compliant substrates are still enjoying a dominant role as the electrode material. This is because of their excellent electrical and optical properties. However, their performance when they are subjected to externally applied mechanical stresses is limited. Such performance has been extensively investigated for the case of continuous brittle oxide films on polymer substrates. However, there is relatively little work reported to date on the mechanical behavior of patterned conducting layers on compliant substrates. Patterned brittle structures may be able to accommodate higher mechanical strains because of their controlled shape, size and edge definition.

In this study we report on the mechanical behavior of various patterned indium tin oxide (ITO) shapes on polyethylene terephthalate. Micron-sized shapes include lines, circles, squares and zigzag-based structures. Uniaxial tensile and buckling experiments are performed in-situ using an optical microscope in order to monitor critical strains and potential failure mechanisms. In addition, in-situ electrical resistance measurements are conducted during mechanical deformation. We also report on the effect of ITO etching time and edge definition. Furthermore, ex-situ characterization using scanning electron and atomic force microscopies is conducted. Finally, experimental results are compared with modeling studies.

We believe that this work is providing an improved understanding that will aid towards designing patterned flexible device platforms with enhanced structural integrity.

Semiconductor quantum dots can confine carriers such as electrons and holes in three-dimensions and exhibit unique electronic and optical properties. For highly efficient IR light-emitting devices using Ge nanodots, a high density of small Ge nanodots, less than 10 nm in diameter, is required. It has been reported that a density of 2×10¹¹ cm² nanodots was achieved by the pregrowth of submonolayer carbon.[1] In this case, carbon atoms were incorporated into a Si(001) substrate and surface strain was induced, leading to the formation of a Si(001) c(4×4) reconstruction structure at the surface layer, which changed the Ge growth from the Stranski–Krastanov (SK) mode to the Volmer-Weber (VW) mode and resulted in formation of a high density of nanodots. Strong repulsive interaction can operate between Ge and C; therefore, Ge atoms deposited on the SiC layer do not interdiffuse. The c(4×4) surface was expected to function as a template substrate for the formation of a high density of Ge nanodots. We have previously reported that the c(4×4) structure is formed by the reaction of monomethylgermane (MMGe) on the Si(001) 2×1 surface. The Ge nanodots embedded in the SiC structure are expected to strongly confine carriers, due to the difference in the bandgap between Ge and SiC. Ge nanodot formation using MMGe resulted in the formation of SiC and Ge nanodots after the appearance of the c(4×4) reconstructed surface. Using a pulse-controlled nucleation method, the formation of a high density (1.3×10¹¹ cm^-2) of nanodots (6 nm) with a small standard deviation (1 nm) was achieved. We have previously reported reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM) results for the surface structure of Ge and SiC nanodots fabricated using MMGe.[2] Photoluminescence (PL) spectra of Ge nanodots capped with a SiC layer were also measured at low temperatures.

In this study, the influence of H-radical irradiation on the photoluminescence properties of Ge/SiC nanodots was investigated. The apparatus configuration and conditions for the growth of Ge/SiC nanodots were the same as those reported previously, except for the addition of a tungsten wire. The tungsten wire (0.2 mm diameter) was heated at 2073 K to generate H-radicals after the growth of Ge/SiC dots and after deposition of the SiC capping layer. The substrate temperature was maintained at 473K-673 K according to the temperature for H-desorption from the Ge-H surface.[3]

Reference s

[1] M. Stoffel et al., Thin Solid Films 380, 32 (2000).

[2] Y. Anezaki et al., Abstracts of the 39^th ICMCTF, San Diego (2012) p. 120.

[3] J. Y. Lee et al., J. Chem. Phys. 118, 1929 (2003).

Glass slides, Au films and (Mg,Zn)O/glass films prepared by chemical spray pyrolysis were used as substrates. The concentration of ZnCl₂ in the aqueous solution was changed in the range from 0.02 to 0.24 M. The pH value of the ZnCl₂ solution was adjusted to 10.0 by adding ammonia water. The concentration of ZnAc was changed in the range from 0.01 to 0.02 M and the molar ratio of HMT to ZnAc was kept at 1:1. The temperature of the water bath was kept at 90°C during the deposition process. Growth time (t_g) was varied in the range from 15 to 240 min.

X-ray diffraction (XRD) measurements and scanning electron microscope (SEM) observations revealed the successful growth of vertically aligned ZnO NRs with preferred c-axis orientation on the Au and (Mg,Zn)O seed layers. When t_g increased from 15 to 180 min, the average diameter of the NRs grown using the ZnCl₂ solution of 0.17 M increased from 150 to 1000 nm together with the change in shape from cones to hexagonal prisms. For the ZnAc solution of 0.03 M, the diameter increased from 100-400 nm for t_g=60 min to 550-1000 nm for 240 min.

PL spectra from the as-grown NRs were composed of an orange (OR) emission and a near-band-edge (NBE) emission. The appearance of the OR emission suggests that the NRs have the high density of interstitial oxygen atom in their surface regions. For the NRs grown using the ZnCl₂ solution, the relative intensity of the NBE emission to the OR emission was independent of tg. For the NRs grown using the ZnAc solution, however, the relative intensity of the NBE emission to the OR emission became larger with increasing t_g, suggesting the improvement of the crystalline quality. PL excitation (PLE) measurements for the NRs grown using the ZnAc solution revealed that the OR emission was effectively excited at the photon energy corresponding to the A free-exciton energy. However, PLE spectra for the OR emission from the NRs grown using the ZnCl₂ solution showed that the secondary phase Zn(OH)₂ formed at the surface regions of the NRs contributed to the excitation process for the OR emission.

In the present work, lanthanum oxide films were deposited by radiofrequency magnetron sputtering from a La₂O₃ target in an Argon atmosphere (20 mTorr). The films were deposited onto Si(100) and glass substrates. Two different RF-powers were tested (60 and 90 watts) and for each power, the deposition time was changed from 25, 40 and 60 minutes, as well as the substrate temperature (ambient and 200°C). The film thickness was measured by profilometry obtaining variations between 102 nm for the 60 W with 25 minutes and ambient temperature and 1097 nm for 90 W with 60 minutes and 200 ºC of temperature. The structure, morphology and chemical composition was studied by X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscopy (SEM), respectively. The optical properties were estimated by modeling the ellipsometric spectra (1.5 to 5 eV) using Tauc-Lorentz dispersion models. The results from the ellipsometric model were compared with the transmission spectra obtained in the UV-VIS range for the films deposited on glass.

Acknowledgements for authors to CONACYT CB-2009, SIP 2012-1303 and PAPIIT IN103910.

Bismuth oxide thin films were deposited by reactive magnetron sputtering from a Bi₂O₃ target (99.95 at%) using RF and an Ar/O₂ atmosphere (80/20). The films were deposited on silicon and glass substrates at 120 W and 150^oC. Under these conditions, the films were stoichiometric and showed the cubic delta phase, which is usually the stable phase of bismuth oxide at high temperatures (725-850^oC). However, as a thin film, it has been shown that the delta-phase can be obtained even at room temperature conditions. The delta Bi₂O₃ is the high ionic conductivity, which is searched for solid oxide fuel cell applications, as the solid electrolyte. The objective of this work is to study the structural stability of the delta-phase films as a function of the both the storage-time and thermal treatments in air. The films were storage under environmental conditions (25^oC, 760 Torr). The film structure was obtained by X-ray diffraction and Raman spectroscopy, which is a very useful technique to identify the presence of the disorder inherent to the delta phase. Similarly, the optical properties have been measured by both transmission and spectroscopic ellipsometry. The films kept at ambient conditions have been analyzed periodically, after a year no changes in the structure have been observed, which is a good indication. Annealing experiments were done in air from 120^oC to 500^oC, in order to identify the temperature at which phase transition occurs. The results indicated that the film structure is stable up 210^oC where the d-phase remained unchanged. Higher temperatures lead to phase transitions into the beta phase up to 360^oC, above this temperature, some regions started to show the alpha-phase. The optical transmission increases with the annealing temperature.

Bismuth oxide (Bi₂O₃) thin films were deposited by Magnetron Sputtering technique under different deposition conditions; substrate temperature and RF power in order to obtain films having different crystalline phases. X-ray diffraction, profilometry, scanning electron microscopy, and optical transmission were used to characterize the films. The results indicated that it was possible to obtain oxide films in the alpha, beta and delta phase, depending on the deposition conditions. The photocatalytic activity for each one of the Bi₂O₃ phases was evaluated testing the degradation of methyl orange dye (C₁₄H₄N₃SO₃Na) under different light energies (ultraviolet, white and solar light). The photocatalytic activity was measured as a function of the irradiation time, light-energy, concentration and pH of the solution. The colorant degradation and the kinetic of the reaction were estimated using the variation of the corresponding absorption band situated at 508 nm (acid media) and 461 nm (neutral and basic media). For the UV light (380 nm and power of 9 W), the results pointed out that the photocatalytic effect was only activated under acidic conditions, for the other pHs, the activity was negligible. Moreover, it was also found that the delta-phase films presented larger photocatalytic efficiency reaching almost 100% of degradation of the dye solution in only 60 minutes, which was an remarkable result considering the photocatalytic performance of other oxides in similar conditions. The rate of reaction of the delta-phase samples was almost twice than that obtained for the other phases. The rate of reaction was used to compare the efficiency of the catalytic reactions and to correlate it with other physicochemical properties, such as the band gap. These results suggest that the Bi₂O₃ films are a rather new and promising photocatalytic material for water treatment application.

Acknowledgement: The research leading to these results has received funding from the European Community Seven Framework Programme (FP7-NMP-2010-EU-MEXICO) and CONACYT under grant agreements nº 263878 and 125141, respectively.

cBN (cubic boron nitride) shows outstanding mechanical properties such as hardness and wear resistance. Despite of the excellent properties, high stress developed during the deposition of cBN film deteriorates adhesive strength of the film and restricts the application for coating material. Recently, addition of hydrogen [1,2] was reported to be useful technique to reduce the residual stress of cBN film prepared by sputtering of B₄C as well as hBN targets. Ar incorporation between (0002) planes of hBN (hexagonal boron nitride) was suggested to be the main origin for the residual stress observed in boron nitride film, which could be suppressed by the hydrogen addition through the formation of sp³ bonding at the growing hBN (0002) plane edge. In this study, we have investigated systematically the effect of substrate bias and hydrogen addition on the residual stress of hBN film prepared by magnetron sputtering of B₄C target. The deposition was performed on Si (100) substrate under the chamber pressure of 0.27 Pa with substrate bias from -200V to -300V. After the deposition of B₄C layer, hBN film was deposited with a step-wise increase of nitrogen flow rate from 0 sccm to 4.5 sccm in Ar/N₂ mixed gas with a constant Ar flow rate of 25 sccm. Hydrogen (5 sccm) was added to a gas mixture of argon and nitrogen flowing 25 sccm and 5 sccm, respectively to investigate hydrogen effect on the residual stress. The compressive residual stress of hBN film was observed to be decreased from 5.0 GPa to 2.8 GPa, with increasing substrate bias voltage from -200V to -300V. The hydrogen addition reduced the compressive residual stress value of hBN film further. The decreasing behavior of the compressive residual stress observed in the hBN film with increasing substrate bias is difficult to be explained only by the effect of lattice defect and distortion induced by ion bombardment. In this presentation, the stress variation with substrate bias and hydrogen addition was discussed in terms of the relation between the penetration probabilities of argon ions into the film.

[1] H.-S. Kim, J.-K. Park, W.-S. Lee and Y.-J. Baik, Thin Solid Films 519 (2011) 7871–7874.

This research was supported by a grant from the Fundamental R&D Program for Core Technology of Materials funded by the Ministry of Knowledge Economy, Republic of Korea

The objective of the present work is to study the co-deformation of composite exhibiting strong mechanical contrast components: nanostructured metallic thin film deposited onto polymeric substrate. The mechanical characterization of such composite structures and the relationship with the microstructure still required for further understanding both for fundamental and technological applications. In order to mimic the stress field of thin films in actual applications, we used a biaxial tensile device dedicated to the DiffAbs beamline at the French synchrotron SOLEIL. The machine allows for controlling equi- or non-equi-biaxial loading onto thin films supported onto compliant substrates, e.g. polyimide substrates. The applied strains are measured in situ both by X-ray diffraction (XRD) and by digital image correlation (DIC). Those two methods are non-destructive: XRD strain is related to the shift of Bragg peaks and DIC strain is obtained from photography of the surface or the backside of the sample. The inherent phase selectivity of XRD technique is a useful tool to get a deeper understanding of the mechanical behaviour of a composite, e.g. the load transfer between the different crystallographic phases and between different orientation grains. The in-situ mechanical testings have been performed onto metallic thin films (produced by Physical Vapor Deposition technique) deposited at the center of a cruciform-shaped polyimide substrate (Kapton ®). In order to verify the accuracy and the feasibility of the combination of the two techniques, the first in situ coupling correlation-diffraction techniques have been performed on W based thin films. Indeed the mechanical modeling using homogenization methods is quite specific for thin films; it has to take into account both the crystallographic texture and morphology of the metallic films. The grain interaction model is very simple in the case a perfect local elastic isotropy such as W. W based thin films allows for directly comparing lattice strains (measured at the microscopic grain scale by X-ray diffraction) to macrostrains (measured at the macroscopic scale by DIC).

Silver coating, particularly prepared by magnetron sputter deposition, has been proven to be antimicrobial and on the way towards commercialization for application in textile industry. However, the expensive raw material and unsatisfactory film adhesion has limited its usage. Copper, on the other hand provides good enough antimicrobial efficacy of all the metals, is considered for silver substitution, but unfortunately suffers poor corrosion resistance in form of thin film coating. Brass, known to be good corrosion resistance, is a good candidate material for antimicrobial coating. The purpose of this study is to obtain an antimicrobial coating starting with brass alloy as target material to grow onto poly(ethylene terephthalate) (PET) textiles by high power impulse magnetron sputtering (HIPIMS), which is known to provide high plasma density, so as to produce strongly adhered film and high quality films at a reduced deposition temperature.

The results show that under a peak target power density of 0.6 kW/cm2, the obtained brass film exhibited layer-by-layer growth mode in the initial stage, followed by island growth mode and reached a film thickness of 238 nm for 10 min deposition. Film composition retained their Cu/Zn ratio (1.86) close to that of brass target, and the phase structure of the film was found to be mainly α-brass. From the results of color fastness to rubbing tests, the film ultimately reached graded 5 and graded 4-5 at dry and wet rubbing, respectively, indicating strong adhesion of the obtained film. Antimicrobial efficacy test show that simply 1 min deposition time can achieve good bactericidal (> 0) and bacteriostatic (> 2.0) efficacy according to the JIS Standard.

Keywords: antimicrobial, poly(ethylene terephthalate), textile, high power impulse

Keywords emulsion, smoke density, acrylic, intumescent

High power impulse magnetron sputtering (HIPIMS) is a novel coating technology, which is characterized for its high peak power density to achieve unique thin film properties, such as high hardness, good adhesion and tribological performance. The aim of this work was to systematically study the microstructure evaluation and mechanical properties of AlCrN coatings as a function of duty cycle and pulse frequency evolutions. The experimental results showed that the peak power density increased linearly as the duty cycle decreaseing from 5% to 1.5%. A maximum peak power density of 2.06kW/cm² was achieved at the duty cycle of 1.5 %. The AlCrN coatings that exhibited a dense microstructure and excellent mechanical properties was fabricated by using the HIPIMS technology under optimal duty cycle and pulse frequency in this work.

Conductive carbon film attracts a great interest for application as electrode materials with its inherent chemical stability in various energy devices such as fuel cell and capacitor etc.. It is well known that conventional deposition processes by plasma including magnetron sputtering and PECVD at low temperature have been limited to synthesize carbon films with high conductivity comparable to that of conductive bulk or powder carbon materials with graphite structure. The design of film structure and process for synthesis of conductive carbon film is performed by energy model deposited onto the surface by control of various plasma parameters in magnetron sputtering, which is closely associated with process parameters. Nano-crystalline(nc) graphite clusters are then synthesized in the matrix of amorphous carbon, and conductivity of the film is therefore significantly enhanced. The conductivity is closely associated with proportion of nc graphite clusters and can be enhanced down to 2x10E-3 ohm.cm in our study.

This paper will discuss on the mechanism of energy deposition at the substrate surface during magnetron sputtering and corresponding changes of nucleation and growth of film with variation of process parameters during magnetron sputtering by integrated plasma diagnostics.

The mechanism of nc carbon film control is then discussed based on the film nucleation and growth theory for designed microstructure of various porosity and corresponding film properties in comparison with empirical data measured for the films deposited by magnetron sputtering with plasma control .