AVS1997 Session TF-MoP: Thin Film Poster Session
Monday, October 20, 1997 5:30 PM in Room Exhibit Hall 1
Monday Afternoon
Time Period MoP Sessions | Topic TF Sessions | Time Periods | Topics | AVS1997 Schedule
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TF-MoP-1 Interfacial Reaction of Thin Film and AlN Ceramic
Y. Wang (Chinese Academy of Sciences, P.R.China); R. Yue (Xian Jiaotong University, P.R.China); C. Chen (Chinese Academy of Sciences, P.R.China) The secondary ion mass spectrometry (SIMS), Rutherford backscattering spectrometry (RBS), Auger electron energy spectroscopy(AES) and X-ray diffraction measurement (XRD) were used to investigate the solid phase reactions between titanium thin film and AlN ceramic substrate during thermal annealing from room temperature(RT) to 850°C. A 200nm Ti film was deposited on a polished AlN at 200°C by electron beam evaporation under ultra high vacuum conditions, and anealed in a vacuum furnace. It has been observed that after annealing above 600°C, diffusion and reaction takes place obviously at the interafce of Ti/AlN, and the interfacial reaction is enhanced with the annealing temperature increase. The titanium aluminides and titanium nitrides as reaction products at interface have been found and the titanium aluminides consist of Ti-Al binary and Ti-Al-N ternary compounds, in which Ti2AlN is dominant after 4 hours annealing at 850°C. The experimnetal results have been explained with Bhansali et al. extended Ti-Al-N ternary phase diagram. *This project was financially supported by National Nature Science Foundation of China. |
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TF-MoP-2 Conductive Oxides Deposited on Polymers with High Transparency in the Solar Window
P. Boy, P. Coquard, M. Firon, P. Hamel, G. Le Blevennec, I. Wartenberg (C.E.A./Le Ripault, France); J.P. Manaud, C. Marcel, J. Salardenne (University of Bordeaux I, France); P. Guerin (University of Poitiers, France) Indium Tin Oxide (ITO) and some others Transparent Conductor Oxides can show an interesting combination of properties: high solar transmittance, high infrared reflectance and good electrical properties. Usually these thin solid films on glass show good spectrally selective properties when they are deposited with substrate temperature ≥250°C or post deposition annealed. In this work, ITO and ITO doped with Germanium (ITGO) have been deposited on thermosensible polymers without heating during process. The optical performances of these films are compared to those obtained on glass at higher temperature. Assisted deposition methods have been used: ion beam sputtering with ion beam assistance and ion beam assisted evaporation. With the first one, the spectrum of ITO deposited on PET shows a solar transmittance of 0.63 and the film has a resistivity of 1.5 10-3 ohm.cm. The second one yields a film deposited on polyimide with a solar transmittance of 0.54 and a resistivity of 10-3 ohm.cm. For larger area applications, the same optical performances have been obtained, at low temperature, by depositing ITO on PET with DC magnetron sputtering and a roll coater system (Reflectivity of 0.80 at 10 µm and solar transmittance near 0.65). To improve the optical characteristics in the solar windows, ITGO has been used. Good optical performances have been observed on glass: solar transmittance of 0.79 and resistivity about 5 10-4 ohm.cm. When deposited by plasma assisted evaporation on polymers, the transmittance in the solar window is 0.71 and the resistivity is about 10-3 ohm.cm. |
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TF-MoP-3 STM and Ellipsometric Characterization of Pt/Ti/Glass Thin Films Deposited by DC Sputtering at Different Temperatures.
J.M. Siqueiros, J. Valenzuela, R. Machorro (Universidad Nacional Autonoma de Mexico); A. Fundora (CICESE-IFUNAM, Mexico); M. Xiao (Universidad Nacional Autonoma de Mexico) Well adhered Pt films were deposited on Ti coated glass substrates by DC sputtering at temperatures between room and 450 °C to optimize its performance as electrodes for ferroelectric devices. Well oriented films in the (111) direction were obtained. STM studies showed an increase in grain size with temperature. The spectroellipsometric studies evidenced a decrease in the packing density of the film as the deposit temperature was risen. A narrowing of the (111) diffraction peak as well as the disappearance of minority phases with temperature was also observed. |
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TF-MoP-4 Microstructural Properties of the BaTiO3 Ceramic in the Bulk and in Thin Films.
A. Fundora (CICESE, Mexico); J.J. Portelles (Universidad de la Habana, Cuba); R. Machorro, G.A. Hirata, J.M. Siqueiros (Universidad Nacional Autonoma de Mexico) BaTiO3 ceramics were obtained by a conventional ceramic method. BaTiO3 thin films were then prepared by pulsed laser deposition on Pt/Ti coated Si (111) substrates. The microstructural properties of the ceramic in the bulk and in thin films were studied and compared using X-ray diffraction, Auger electron spectroscopy, XPS and scanning electron microscopy. The differences in the structural and dielectric properties of the ferroelectric films as compared with the bulk are discussed. |
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TF-MoP-5 Pulsed Laser Deposition of (Pb,La)(Zr,Ti)O3 Ferroelectric Thin Films on Si Substrates in Waveguide Form
S.B. Xiong, Z.G. Liu, T. Yu, D. Zhang, S.N. Zhu (Nanjing University, P.R. China); W.G. Luo (Chinese Academy of Science, P.R. China); C.L. Chen (Superconductor Center of Houston University) Ferroelectric (Pb, La) (Zr,Ti)O3 (PLZT(9.4/65/35)) optical waveguiding thin films have been prepared on MgO/SiO2 bilayer coated Si and on silica glass substrates by pulsed laser deposition. X-ray θ -2θ scans revealed that the films are single-phase pseudo-cubic perovskite. The surface chemical composition of the as- grown films was determined by XPS. The ferroelectric properties of the films as grown on Pt/Ti coated silicon were demonstrated by using a modified Sawyer-Tower circuit, and the optical waveguiding properties of the films were characterized by using a rutile prism coupling method. The as grown films have an average transmittance of 80% in the wavelength range of 400~2000nm and a refractive index of 2.2 at 632.8nm close to the bulk PLZT. The distinct m-lines of the guided TM and TE modes of the films as grown on MgO/SiO2 coated Si substrates have been observed. |
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TF-MoP-6 In-Situ TEM Observations of Strain Relaxation and Dislocation Formation during SiGe/Si Heteroepitaxy
Y. Hiroyama, M. Tamura (JRCAT-ATP, Japan) An ultra-high vacuum transmission-electron microscope equipped with a conventional molecular-beam epitaxy chamber (UHV-TEM/MBE) has been constructed in order to do in-situ observations of SiGe/Si heteroepitaxial growth. The UHV-TEM/MBE system consists of four chambers, that is, an UHV-TEM (based on a Hitachi UHV-H9000), UHV-TEM transfer, UHV-TEM/MBE exchange, and MBE growth chamber, as well as two preparation chambers. Samples were successively transferred from the MBE growth chamber to UHV-TEM chamber and vise versa, through exchange and transfer chambers under a pressure of less than 1x10-9 Torr. It is possible to observe the same region in a sample after a sequence of the sample transfer and the repeated MBE growth. The Ge fraction of x (Si1-xGex) was varied at x= 0.3, 0.7 and 1. Substrate orientations were also varied for pure Ge growth. The main results obtained so far are as follows: (1) The moiré-fringe spacing of the films observed at every growth stage was wider than that expected from the bulk lattice parameters of Si and SiGe, which suggests that the misfit strain is not completely relaxed below the thickness of 100 ML at 550°C by the generation of misfit dislocations. (2) It was shown by the discontinuity of moiré-fringes that lattice defects are formed at the boundaries of coalesced islands above the thickness of 25 ML. (3) Strain relaxation began at the center of strained islands and spread to the edge of islands. *This work, partly supported by NEDO, was performed in the JRCAT under the joint research agreement between the NAIR and the ATP. |
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TF-MoP-7 Modeling of Titanium Oxide Deposition by Reactive Ion Beam Sputtering
G. Ravel, M. Berger (LETI.CEA, France) The work presented here is our first attempt to quantitatively describe oxide deposition by reactive sputtering in an industrial ion beam system used for multilayer optical thin films. The model is based on material balance on target and substrate holder surfaces. From a detailed analysis of the geometry of the chamber, substrate holder, ion source and target location, we derive geometrical characteristics of the deposition system. Emission law for titanium target bombarded by 1 keV xenon ions is established by static deposition rate measurements. Sputtering yield of Ti by Xe is estimated; a simple model for incidence and energy dependence allows to compare experimental value to literature. An assumption is made about the emission law of oxide layer on the target (poisoned area), to calculate the contribution of this flux to the global flux incoming to the substrate: the emission is supposed to occur in a similar way to titanium emission. This point is verified by the comparison of static deposition rate profile for titanium and titanium oxide. Non linear relationship is calculated between oxygen flow and pressure: no instability of process is to be found, owing to the very high pumping speed typical of ion source vacuum systems. Deposition rates and compositions of the deposit as functions of oxygen pressure and ion current are calculated over the substrate holder surface, showing strong gradients for low oxygen flows. Predicted composition changes with oxygen pressure are compared with values obtained by RBS measurements, showing a reasonable agreement. According to our calculations, the best conditions of operation (quasi-perfect stoichiometry) occur with an almost entirely oxidized target surface. Of course, these conditions may very well be typical of our system, as far as oxygen inlet location and pumping features are concerned. Modeling is eventually extended to the practical case of dynamic deposition onto a planetary system, leading to a global prediction of actual deposition rates for titanium oxide layers. |
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TF-MoP-8 Studies on Electrical, Mechanical and Compositional Properties of WSix Thin Films Produced by Low Pressure Chemical Vacuum Deposition.
S. Santucci, P. Petricola, L. Lozzi, P. Picozzi (Universita' dell'Aquila, Italy); G. Moccia, R. Diamanti, R. Alfonsetti (Texas Instruments Italia - Consorzio EAGLE, Italy) Tungsten silicide (WSix) thin films of thicknessess of 1500 Å have been deposited by Low Pressure Chemical Vapour Deposition using Silane (SiH4) and Tungsten Hexafluoride (WF6) at different fluxes ratio ranging from 100 to 800. Since these films find application as "control gate" electrode in the FLASH memory production line, they have been deposited onto planar substrates consisting of electronic grade 6" Si <100> wafers covered by 100Å of SiO2 and 1000 Å of phosphorus -doped poly-silicon layers to reproduce the control gate structure. The deposited films have been treated for annealing in oxygen ambient at 850 C. The properties of as deposited as well as annealed films have been studied by different techniques. X-ray Photoelectron Spectroscopy (XPS) and Rutherford Backscattering Spectroscopy (RBS) have been carried out to study the composition of the films. Thickness of the films has been measured by cross section Scanning Electron Microscopy (SEM) which in turn compared with the results obtained by RBS. Resistivity of the films has been measured by a four probe sheet resistance method. The mechanical properties of the films have been measured by a laser based stress technique. The as deposited films have shown , growing the SiH4/WF6 ratio, an increase of Si/W stoichiometric ratio (until 3), the decrease in film thickness and stress while there is an increase in sheet resistance.In the case of annealed films, which pass from amorphous state to crystalline structure, as detected by X-Ray Diffraction (XRD), there is a strong decrease of the sheet resistance values as well as film thickness, together with a slight increase of the stress values dependent on the SiH4/WF6 ratio. The presence of silicon oxide layer with different thickness has been also detected on the surface of the silicide films. Finally in the annealed films the WSix layer contains lower silicon in comparison with the as deposited samples, whereas the surface morphology, studied by Atomic Force Microscopy, showed a decrease in the surface roughness. |
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TF-MoP-9 In/Si(001): One-Dimensional Island Formation Studied by STM and Modeling
M.M.R. Evans, J. Nogami (University of Wisconsin, Milwaukee) Submonolayers of indium deposited on the Si(001) surface form single atom wide rows of atoms. We have studied the length distribution of these rows in detail and found that this system is a good test case for island growth theories since each row consists of a countable number of atoms. The row length distributions at different coverages collapse onto a single scaled curve in agreement with the theory of Bartelt and Evans1, but the form of the scaled curve differs from theirs, and from other calculated results. Our own Monte Carlo simulations agree qualitatively with our data. We hope to use the simulations to explore the effects of anisotropic accommodation, anisotropic diffusion, and of 1D island configuration on growth, and to explain the discrepancies with prior models.
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TF-MoP-10 Sputtered Vanadium Oxide Thin Films for Gas Sensor Characterized by Atomic Force Microscopy
A. Cricenti, R. Generosi, M. Girasole (Consiglio Nazionale delle Ricerche, Italy); C. Coluzza (Universita' di Roma La Sapienza, Italy); R. Rella, P. Siciliano (Consiglio Nazionale delle Ricerche, Italy); M. DiGiulio (Universita' di Lecce, Italy) Ethanol detectors realized by Vanadium Oxide (V2O5) thin films have been characterizated by Atomic Force Microscopy (AFM). The films were prepared by means of r.f. reactive sputtering technique, with different concentrations of oxygen in the atmosphere of growth; after the deposition the sample were divided into two part: half of them were thermally treated and the other half were not. This allow to test the effect of warming that is a useful way to enhance the performance of the gas sensors. The AFM measurements were performed in air and have been discussed in terms of surface roughness. The results show that, for both treated and untreated samples, the roughness increases with increasing percentage of oxygen in the atmosphere of growth but with the singularity of the samples with the best sensing properties (15% of oxygen) that evidentiates a characteristic minima. Moreover, we observe that the thermal treatment also determines a general decreasing of roughness especially marked in samples with low percentage of oxygen. |
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TF-MoP-11 STM Studies of Pinehole Formation in Thin Film CoSi2
L. Ruan, D.M. Chen (Rowland Institute for Science) Owing to its low contact resistance and small lattice mismatch with a silicon substrate, CoSi2 has been one of the prime candidates for the silidation process in ULSI circuits fabrication. A good crystalline quality of CoSi2 film with a low resistance can be achieved by rapid thermal annealing of deposited Co on a Si substrate. Unfortunately, this process normally generates large pinholes in the silicide film, a problem that can seriously affect our ability to further downsize the ULSI devices. In attempt to understand the microscopic origin of the pinhole formation associated with the annealing process we have performed a detailed study of a CoSi2 film formed by annealing 4-10 Å Co deposited on a Si(111) in an UHV chamber using STM, AES and LEED. It was found that the as-deposited film has a uniform granule (30-60 Å) structure, presumed a Co-Si mixture. Rapid annealing at 590 °C produces an epitaxial CoSi2 film whose steps resemble those of the original substrate. Triangle and hexagonal pinholes were observed to have a depth of 30-150 Å, much deeper than the interface. Interestingly, each pinhole is surrounded by CoSi2 islands, 1-3 layer higher than the terraces, forming a volcano feature. Quantitative measurements show that silicon atoms removed from the pinhole region directly contribute to the formation of adjacent CoSi2 islands, suggesting that reaction of Co and Si at the outer surface is partially responsible for the pinhole formation. Higher temperature (700 °C) annealing results in the dewetting of CoSi2 layers to form an undesirable percolated film. |
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TF-MoP-12 Measurement and Modeling of Angular Distributions of Sputtered Atoms in Planar Magnetron Discharges
L. Zhu, K.A. Cowen, R.S. Bailey, N.C. Hill (Tosoh SMD, Inc.); B. Philips (Zilog Inc.) The angular distribution of sputtered atoms in a planar magnetron discharge have been measured from various target materials using a specially designed research sputtering tool, incorporating a directional RGA detector. The sputtering target materials investigated here include, Al, Ti, and Cu. Experimental polycrystalline, and single crystal, sputtering targets (50 mm diam.) were produced with different crystallographic textures/orientations. These measured distributions are compared with the results from a model which predicts the angular sputter yield from the crystallographic texture measured for each target, assuming certain preferred crystallographic emission directions. Monte Carlo PVD simulations were made using the angular sputter yield distributions. Calculated film thickness uniformity and via fill agree with the experimentally measured values. Results from conventional PVD systems (200 mm wafer size) were also studied here. Experimental targets were produced with different textures, and radial texture gradients. Films sputtered from these targets showed significant differences in thickness distribution across the wafer diameter, agreeing with the predictions from the model. The tools developed here are used to estimate the maximum improvements possible, in film uniformity and via fill, through control of target crystallographic texture. The effects of the sputtering system parameters (target erosion profile, target-substrate spacing, gas pressure, etc.) were also studied. |
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TF-MoP-13 Film Properties of ZnO:In Prepared by Facing Target Sputtering of ZnO:In Targets and Zn Target
K. Tominaga, N. Umezu, I. Mori, H. Manabe, T. Ushiro, T. Moriga, I. Nakabayashi (The University of Tokushima, Japan) ZnO:In films were prepared by a sputtering method with facing targets. Optimal conditions with regard to impurity doping level in indium oxide and in substrate temperature were investigated; Electrical data showed that the lowest film resistivity is prepared at a substrate temperature of 150 C using a ZnO target doped with 3 wt% In2O3. At high substrate temperatures above 300 C the film resistivity increased as the carrier concentration decreased. The carrier concentration had a maximum at a substrate temperature of 150 C, whereas the Hall mobility was nearly constant. This indicates a significant decrease in the doping efficiency of indium as donor, ascribed to the evaporation of indium donor impurity during the film growth. This was also confirmed by XPS measuremnt and infrared absorption measurement for the film. The doping mechanism of indium in ZnO:In film was investigated further by adding additional Zn during the ZnO:In film deposition and comparing the results with the data for ZnO:Al films. For the films deposited at 150 C, carrier concentration slightly increased with the addition of Zn. For the films prepared at above 250 C, carrier concentration decreased under the same Zn addition, but further addition of Zn atoms increased the carrier concentration again, due to an increase of native donors. The dependence of the carrier concentration on the addition of Zn is understood by a decrease of doping efficiency as well as the generation of native donor. This trend is inverse to that of ZnO:Al film. |
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TF-MoP-14 P-Type Transparent Conducting In2O3-Ag2O Thin Films Prepared by R.F. Magnetron Sputtering
T. Minami, K. Shimokawa, T. Miyata (Kanazawa Institute of Technology, Japan) Although transparent conducting oxide (TCO) films which are n-type semiconductors, such as ITO, SnO2 and ZnO have been widely used, there are few reports about the preparation of p-type TCO films. This paper introduces a new TCO film, a p-type wide gap semiconductor prepared by rf magnetron sputtering. The sputter deposition was carried out in a pure argon sputter gas using In2O3 targets with a Ag2O content of 0 to 100wt%. In2O3-Ag2O films with a thickness of about 300 nm were prepared on glass substrates at room temperature. The resistivity of In2O3-Ag2O films increased markedly as the target Ag2O content was increased from 0 to about 30wt%, but with a further increase of Ag2O contents above about 40wt%, it then decreased. The as-deposited In2O3-Ag2O films prepared with Ag2O contents of 40 to 60wt% showed p-type conduction, but the resistivity of these films was relatively high. In contrast, when postannealed at 500°C in air, these films exhibited high levels of p-type conduction as well as transparency. A hole concentration on the order of 1019cm-3 was obtained in the postannealed films, as evidenced by van der Pauw measurements. From X-ray diffraction analyses, the as-deposited and postannealed In2O3-Ag2O films were found to be amorphous. A minimum resistivity of 8.8x10-3Ωcm and an average transmittance above 27% in the visible range were obtained in p-type amorphous In2O3-Ag2O films prepared with an Ag2O content of 50wt%. |
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TF-MoP-15 Studies on Anti-Glare, Anti-Static and Transparent Conductive Film on Display Tubes
G.K. Xi, G.H. Zhang, S.L. Li, S.M. Shao, W. Guo, X.J. He (Nankai University, China) Anti-glare,anti-static thin film and transparent conductive film are widely used in many fields of production, science and technology, such as solar cell,TV image display panel, instrument panel and transparent electrode. Anti-glare and anti-static double-layered coating on ordinary glass prepared by a sol-gel technique is introduced. The outer layer of low refractive index is coated on high refractive index inner layer. The main composi- tion of outer layer is SiO2. Some SnCl4 added into this film increases the conductivity of this film. The latter can be replaced by other hygroscopic metal salts,such as Al(NO3) 3,AlCl3,ZnCl2, etc.. The inner layer is composed of TiO2 and SiO2. The glass panel with the double-la- yered coating shows the resistivity of 109 Ω/square and reflectance of 1.6 % which is reduced to one-fourth of that without coating. A transparent film with high conductivity on ordinary glass panel prepared by a sol-gel technique is also intro- duced. This Sb-doped SnO2 film is made from alkoxide which was previously prepared in our lab. This ATO film has a polycrys- tall structure. The resistivity of the ATO film has minimum value of 103 Ω/square while the doping level of the solu- tion is about 7%. Finally,factors such as enviromental temperature and humidity,coating technology,effecting the characteristics of these films are discussed. |
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TF-MoP-16 In Situ Observation of Hydrogenated Amorphous Silicon Surface during Electron Cyclotron Resonance Hydrogen Plasma Annealing using Polarization Modulation Infrared Reflection Absorption Spectroscopy
R. Nozawa, H. Takeda, M. Nakamura, K. Murata, M. Ito, M. Hori, T. Goto (Nagoya University, Japan) The surface reaction of hydrogenated amorphous silicon (a-Si:H) films during electron cyclotron resonance (ECR) hydrogen (H2) plasma annealing has been investigated by in situ polarization modulation infrared reflection absorption spectroscopy (PM-IR-RAS). The a-Si:H films were deposited on Al/c-Si substrates by ECR SiH4/H2 plasma at a total pressure of 0.53Pa, a microwave power of 300W, a flow rate of SiH4/H2: 10/100sccm. The deposition temperature was varied from room temperature (RT) to 250 C to form a-Si:H films with various compositions of Si-Hx (x≤3) bonds. The a-Si:H films formed at various substrate temperatures were exposed by ECR deuterium (D2) plasma at a total pressure of 0.53Pa, a microwave power of 300W, a D2 flow rate of 100sccm. The substrate dc bias was varied from -50V to +50V to control the energy of ions incident on the substrate. Moreover, permanent magnets were set above the substrate to shut out charged species incident on the substrate and so atomic deuteriums were supplied to the a-Si:H surface. The surface reaction of a-Si:H films by atomic deuterium annealing was observed by PM-IR-RAS and the results were compared with those by ECR D2 plasma annealing. It was found that atomic deuteriums reacted with the Si-H2 and (SiH2)n bonds near the surface and that the etching effects were not observed at an annealing temperature of RT. Atomic deuteriums permeated into the bulk of a-Si:H film and promoted the Si-network modification as the annealing temperature increased. These results were the same as those at +50V in ECR D2 plasma. On the other hand, at -50V, the etching reaction of a-Si:H was successfully observed during ECR D2 plasma by PM-IR-RAS. |
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TF-MoP-19 Chiral Thin Films For Flat Panel Displays
K. Robbie, M.J. Brett (University of Alberta, Canada) Chiral thin solid films with optical properties similar to cholesteric liquid crystals (CLCs) have been fabricated and investigated with transmission ellipsometry. Glancing angle deposition (GLAD) 1 was used to "sculpt" thin film columnar microstructure into helical shapes with control on the sub-10 nm scale and with helical pitches on the order of the wavelength of visible light. Transmission ellipsometry measurements of optical rotatory dispersion 2 have confirmed that these helical structured films have optical properties very similar to those of CLCs with strong features in a narrow wavelength zone and peak optical rotations of about 350 degrees/mm 3. From comparisons with CLCs and the theory of helicoidal bianisotropic media 4 we expect that these films will exhibit circular Bragg reflection (the effect exploited in cholesteric liquid crystal displays - Ch-LCDs) where one incident circular polarization state is preferentially reflected while the other is transmitted. A solid analog of CLCs is desirable because of the delicate nature and limited range of CLCs. Helical thin films have been fabricated with GLAD with pitches ranging from 50 nm to greater than 2 microns in metals, metal oxides and fluorides, and semiconductors and conceivably could be fabricated of almost any vacuum depositable material. The large range of control over the film microstructure is also very useful. For example, to increase the reflection bandwidth in CLCs a pitch gradient is created with a complicated diffusion polymerization process while with thin films fabricated with GLAD, a simple change in the deposition control software can create a pitch gradient.
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