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We show that the chemical sensing responses of organic field-effect transistors based on nanostructured regioregular polythiophene are strongly dependent upon the gate biasing field. With different applied gate voltages, the source-drain current response can be different both in sign and magnitude for the same analyte. This implies that multiple competing sensing mechanisms exist at the same time. We propose that the sensing mechanisms for polycrystalline semiconducting polymer thin films are mainly an intragrain effect, which yields a positive response, and a grain boundary effect, which yields a negative response.

Multiple regioregular polythiophene polymers with a variety of side chains, end groups and secondary polymer chains were used as active sensing layers in a single chip chemresistor sensor array device. A custom inkjet system was used to selectively deposit the polymers onto the array of transduction electrodes. The sensor demonstrated sensitivity and selectivity for detection and discrimination of volatile organic compounds (VOCs). The conductivity responses to VOC vapors are dependent on the chemical structure of the polymers. For certain VOCs, conductivity increased in some polymers, while it decreased in others. Principal component analysis (PCA) of sensor responses was used to discriminate between the tested VOCs. These results are correlated to the chemical structures of the different polymers, and qualitative hypothesis of chemical sensing mechanisms are proposed. This research demonstrates the potential for using such devices in VOC detection and discrimination sensing applications.

In this work, Ag underlayers, which have a slightly larger lattice parameter than FePt, were found not only to induce epitaxial growth of the FePt films but also to reduce the temperature at which the atomic ordering occurred. Without using the Ag underlayer, the FePt film deposited onto the hydrofluoric acid etched-Si substrate was FCC disordered. When Ag underlayers were used the FePt unit cells were expanded in the film plane. This caused the shrinkage of the FePt unit cells along the film normal direction and resulted in the in situ ordering of the FePt thin film at reduced temperatures. Furthermore, it was found that the degree to which the FePt unit cells contracted along the film normal varied when a Pt intermediate layer was added. This resulted in FePt thin films with different textures and magnetic properties. The microstructural and magnetic properties of the FePt films prepared at various substrate temperatures, FePt thicknesses, Ag underlayer thicknesses and with the use of the Pt intermediate layer were studied to investigate the L10 FePt ordering.

We describe a new Ni/sub 5/Al/sub 3/ underlayer for high-density longitudinal magnetic recording. The Ni/sub 5/Al/sub 3/ underlayer has the FCC derivative Ga/sub 3/Pt/sub 5/ structure. The Ni/sub 5/Al/sub 3/ [221] plane has good lattice match with the CoCrPt (101~0) plane. In addition, unlike the NiAl [112] plane, the Ni/sub 5/Al/sub 3/ [221] plane has the lowest surface energy. Hence, the Ni/sub 5/Al/sub 3/ thin film has a strong [221] texture and can induce CoCrPt (101~0) texture. The microstructure and magnetic properties of the CoCrPt-Ni/sub 5/Al/sub 3/ thin films are reported and discussed.

Post-deposition rapid thermal annealing (RTA) was performed on the Cr-less Co-20 at%Pt alloy with a Mn diffusion layer on top. A Ku value of about 8/spl times/10/sup 6/ erg/cm/sup 3/ was obtained for the as-deposited film and it decreased only up to about 10% after annealing. The high intergranular exchange coupling of the as-deposited CoPt film was suppressed by RTA and the coercivity increased dramatically from about 2200 to 6000 Oe. The energy-filtered TEM plane-view images showed depletion of Co and aggregation of Mn at the CoPt grain boundaries. This is a direct evidence supporting preferential diffusion of materials from adjacent layers into magnetic grain boundaries.

While spin valve transducer technology may be extendible beyond the 100 Gbit/in2 regime, isotropic longitudinal media will show large data retention problems at about 1 3 of this value. We have recently developed a simple model which indicates that while thermal instability issues may appear at different areal densities, they are non-discriminatory as to the magnetic recording modality: longitudinal, perpendicular, magnetooptic, near field, etc. The model indicates that strong orientation of the media tends to abate the onset of the thermal limit. For the past few years we have taken an approach of controlled growth of the magnetic microstructure of thin-film media. This knowledge has lead us to believe that epitaxial growth of multiple thin-film layers on single crystalline Si may provide a pathway to nearly perfect crystallites of various, highly oriented, thin-film textures. Here we provide an overview of the recording system media challenges, which are guiding our media design philosophy, and discuss materials issues and processing techniques for multi-layered thin film material structures which may be used to achieve very high degrees of Co-alloy film orientation.

Various aspects of the structure of thin film longitudinal recording media are presented and discussed. In particular we discuss the role that the various layers of thin film media play in controlling the microstructure and magnetic properties of the magnetic layer. These include the grain size of the films, the texture of the films, the role of the intermediate layer and the role of chemical segregation.

In this paper several different schemes for multilayered longitudinal magnetic recording media are presented and discussed. We will focus the discussion on those schemes on which we have worked over the past several years, emphasizing the role of new underlayers, seed layers, intermediate layers and interlayers. In each case we discuss the role that each of the layers plays in determining the important magnetic properties and recording performance of the Co based hcp thin film media. Included in the paper is a review of the role of new underlayers (NiAl and MgO), seed layers (MgO), intermediate layers (Cr, Co alloys) and interlayers (Cr, Al, Cu and Ag). Throughout we discuss the role of epitaxy between the various layers and demonstrate that the resulting microstructure and crystallographic texture of the films depends strongly on such epitaxy. These characteristics, in turn, control the resulting magnetic properties of the Co based films such as in plane coercivity H c and squareness ratio, S ∗ .

In this overview we summarize our methods of changing important microstructural features such as grain size and crystallographic texture, in magnetic thin films for longitudinal recording. The methods we have used to better control the grain size and texture of the magnetic films include the use of different underlayers (NiAl and FeAl), the use of seed layers underneath the underlayers and the use of intermediate layers between the underlayer and the magnetic thin film. Examples of the structure and magnetic properties of such films will be presented and discussed. We also present our newly developed method of quantitatively characterizing the crystallographic textures of the thin films used in the multilayered structures. Our method relies on the examination of the intensity weighted reciprocal lattice by means of tilted electron beam diffraction patterns. These patterns contain arcs, the number and location of which can be correlated with specific thin film textures. We will present an overview of the technique from the point of view of the reciprocal lattice and include an example which shows how the crystallographic texture of thin films can be examined and characterized.

Extrinsic magnetic properties play a major role in determining the performance of magnetic thin films used as magnetic recording media. These extrinsic properties are the ones which are largely determined by the microstructure of the thin magnetic films. In this paper we discuss various ways that the crystallographic texture of thin films can be controlled. We begin with a discussion of the origin of crystallographic texture of underlayers. Next, the origin of crystallographic texture of magnetic thin films by means of epitaxy with the underlayer is discussed. The control of other microstructural features such as grain size and perfection by means of underlayers and interlayers is briefly introduced. Examples from recent research are included.

In this study, we correlate various processing conditions with the magnetic properties of CoCrTa/Cr films by varying the substrate preheating, the substrate bias, and the composition of the magnetic target. High Hc CoCrTa/Cr films with thin Cr underlayers were produced by either preheating the substrate or by rf bias sputtering. We found that the sputtering temperature of the magnetic layer plays a far more important role in reducing intergranular exchange coupling and increasing Hc than does the CoCrTa/Cr crystallographic texture. The optimum condition for preparing high Hc films depends on the magnetic target composition. Even though the crystallographic texture does not control Hc, it does have an effect on the ΔM curve which is related to the noise properties of CoCrTa/Cr media. ΔM measurements indicate that {1101}Co /{110}Cr textured films may have slightly better noise properties than the films with {1120}Co /{200}Cr texture with similar Hc.

Although it is well known that Cr underlayers sputter deposited on glass or NiP/Al substrates have either the (002) or (110) textures, the mechanism of the formation of the crystallographic textures is not clear. A model is proposed for the formation of the crystallographic texture of sputter‐deposited Cr thin films. A systematic set of experiments has been carried out to test the model. It was found that the (110) texture, which is usually found in Cr thin films deposited on substrates without preheating, can form at elevated temperatures (250 °C) when deposited at low Ar pressure or by applying substrate bias. The initial stage of the texture formation was also investigated by using very thin Cr films. It was found that the (002) texture can be initiated directly on the substrate surface, while the (110) texture appears not to form directly on substrate surface, but rather as a result of film growth. The proposed model is consistent with the experimental results.

A new reflected mode magneto‐optic spatial light modulator (R‐MOSLM) has been developed for miniature optical correlators and computers. A factor of 4 improvement in pixel switching sensitivity, compared to the conventional transmission mode magneto‐optic spatial light modulator, has been achieved by the use of narrower drive lines, and burying the conductor into the film. A factor of 3 higher resolution and a factor of 2 higher optical efficiency have also been achieved by the use of smaller pixels and narrower pixel gaps. The smaller pixels and improved switching sensitivity permit an order of magnitude reduction in optical path length and increase in frame rate, respectively. The progress that has been made in the design of the R‐MOSLM, issues concerning its fabrication, a comparison by finite element analysis of field modeling to experimentally determined current requirements to drive individual lines, and some optical characteristics are discussed.

We have fabricated and demonstrated the operation of electro-optic beam deflectors using domain reversal in planar waveguides fabricated on LiTaO/sub 3/ substrates. The planar waveguides were made using proton exchange on z-cut substrates, and proton exchange with subsequent rapid thermal annealing was used to form the inverted domains. The deflection sensitivity of the device was measured to be about 6.7 mrad/kV. Calculations indicate that the deflection sensitivity should be increased by a factor of 25 to 30 with improvements in device geometry. >

Stacking faults in (101~0) unicrystal Co and Co-alloy thin films have been analyzed by the electron diffraction technique. As predicted no diffraction contrast of stacking faults could be observed when the beam is parallel to the [101~0] direction. However, both by plan-view TEM observation and electron diffraction along the [112~0] direction reveal that the stacking fault density in biased pore Co (101~0) Bin films is much lower than that in unbiased ones. The addition of Cr in Co films significantly reduces stacking fault density whereas the addition of 8 at% Pt leads to a considerable increase in stacking fault density. Our results show that stacking faults in Co thin films significantly, and negatively, affect the anisotropy energy density and its temperature dependence.

In this work Ag underlayers, with a slightly larger unit cell than FePt, were found not only to induce epitaxial growth of the FePt films but also to reduce the FePt ordering temperature. Without using the Ag underlayer, the FePt film deposited onto the Si substrate was fcc disordered. By the use of the Ag underlayer, it was observed that the FePt unit cells were expanded in the film plane. This has caused the shrinkage of the FePt unit cells along the film normal direction and resulted in the in situ ordering of the FePt thin film at reduced temperatures. The microstructural and magnetic properties of the FePt/Ag films at varied substrate temperature and FePt thickness were studied to investigate the L10 FePt ordering.

Highly oriented soft underlayers with face-centered-cubic (fcc) phase Co, Co alloy, and composite NiFe/Co film structures have been epitaxially grown on single crystal Si wafers by sputter deposition. The epitaxial orientation relationships have been determined by x-ray diffraction and transmission electron microscopy. It was found that the soft underlayer magnetic properties can be modified in a wide range by fine tuning the Co alloy composition or the Co alloy thickness in a NiFe/Co structure. Ti films were sputter deposited on top of the NiFe and Co layers and epitaxial growth in both Ti(0001)/Co(111) and Ti(0001)/NiFe(111) was observed. Through this highly oriented Ti intermediate layer, a Co alloy perpendicular media layer with greatly improved hexagonal-close-packed (0001) orientation can be integrated with the highly (111) textured fcc soft magnetic underlayers.

Anodization experiments to create alumina pores were performed using pure Al and hard disk Al–Mg substrates. A single step anodization was employed for up to 40 h to determine the time dependence of pore ordering. The pores formed from the Al–Mg substrate were unordered, while ordered-pore domains as large as 3 μm form in both the as-rolled and annealed pure Al samples. The effect of the aluminum grain crystallographic orientation was investigated via orientation-imaging microscopy for the pure Al surface with both order and disordered pores. It was found that neither heat treatment nor crystallographic orientation played a large role in the pore ordering.

Post-deposition rapid thermal annealing (RTA) was performed on multilayered films consisting of a Mn capping layer on top of CoCrPt/CrTi/NiAl. High coercivities were achieved even at low Mrt values and coercivity values increased more than that would have been predicted by the decrease in magnetization values. This is most likely due to the significant decrease in intergranular exchange coupling, as shown by the δM measurement. Transmission electron microscopy characterization indicates no apparent grain growth and no visible improvement in CoCrPt crystallographic texture after RTA. It is believed that the preferential diffusion of Mn into CoCrPt grain boundaries promotes magnetic grain isolation.

The dependence of the Co anisotropy constants on the measurement temperature, deposition conditions, and underlayer materials was studied using unicrystal Co(1010)/Cr (or NiAl)(112)/Ag(110) films sputter deposited on hydrofluoric acid etched Si(110) substrates. The single, in-plane easy axis orientation in these films allows the direct determination of the anisotropy constants. The anisotropy constants of unicrystal Co films are smaller than those of a bulk Co single crystal, and the temperature dependence of the anisotropy constants is stronger. The K1 value drops by 50% as the temperature is increased from 25 °C to 75 °C, and then becomes negative at 135 °C. This zero-crossing temperature is considerably lower than the 250 °C at which K1 of a bulk Co single crystal decreases to zero. The anisotropy constants also vary with the film preparation substrate temperature. Applying a substrate bias during the Co deposition effectively increases K1 to near bulk material values. Unicrystal Co films grown on NiA...

Mn3Si possesses a D03 structure, which is a bcc derivative structure with nearly the same atomic spacing as Cr and NiAl which have been commonly used for longitudinal magnetic recording underlayers. AG(30 nm)/CoCrTa(40 nm)/Mn3Si(x, x=100, 200, 400 nm)/Ag(75 nm) thin films were sputter deposited onto hydrofluoric acid (HF)-etched Si:(001) substrates at elevated temperature. Compared to the 100 and 200 nm thick Mn3Si samples, the XRD spectrum of the 400 nm thick Mn3Si sample shows a significant increase in the intensity of the Mn3Si(002) peak. This suggests that a high volume fraction of the D03 phase was formed. The CoCrTa(1120) peak intensity has been found to increase with Mn3Si thickness. As a result, the in-plane coercivity increases as the volume fraction of the D03 phase increases.

Application of reflection high-energy electron diffraction (RHEED) to texture determination is demonstrated for magnetic thin film applications. Diffraction pattern analysis based on kinematic theory of RHEED is outlined. Application of the technique is demonstrated for texture characterization of hexagonal-close-packed CoCr alloys that are used as recording layers in perpendicular recording media. It is shown that both texture orientation and texture angular dispersion extracted from RHEED patterns are in agreement with the data obtained using x-ray diffraction.

In situ ordering of FePt thin films by sputtering onto Ag/Si and Ag/Mn/sub 3/Si/Ag/Si templates has been demonstrated. Due to the evolution from island-like to a continuous film structure as a function of Ag thickness, the ordering and orientation of the FePt films both change with Ag thickness. A continuous [002] Ag film results in a greater L1/sub 0/ phase formation with c-axis oriented both perpendicular to and in the film plane while the island-like Ag template results in less L1/sub 0/ phase formation, but a preferential c-axis orientation in the film plane. On the other hand, the FePt films deposited onto the Ag/Mn/sub 3/Si/Ag/Si template have their c axes aligned perpendicular to the film plane.

In this paper, we show that the chemical sensing responses of organic thin film transistors (OTFTs) based on nanostructured regioregular polythiophene are strongly dependent upon the gate biasing field and the operation mode. With different applied gate voltages the source-drain current response can be different both in sign and magnitude for the same analyte. Using swept gate voltages, sensors show larger response than when operated with a constant gate voltage. These results imply that multiple, competing sensing mechanisms exist. We propose that the sensing mechanisms for polycrystalline semiconducting polymer thin films are mainly an intragrain effect, which yields a positive response, and a grain boundary effect, which yields a negative response. Noise properties of the OTFT sensors were also investigated. For the typical sensor operation frequency range these results show that low frequency noise is the dominant noise source.

Quad-crystal CO-alloy/Cr/Ag thin film media were epitaxially grown on hydrofluric acid etched Si(111) single crystal substrates by sputter deposition. The orientation relationship was studied by x-ray θ/2θ diffraction and pole figure Φ-scan, and it was determined to be Co(1011) || Cr(ll0) || Ag(111) || Si(111). The Ag layer contains two twin-related orientations of grains. Cr grows with three variants of grains on the Ag(111) layer. Since Co(1011) contains grains with four possible easy axis directions when grown on each Cr variant, the quad-crystal media consist of grains with twelve easy axis directions and exhibit nearly isotropic in-plane magnetic properties.

The magnetic properties of CrPt3 L12 ferrimagnetic thin films have been studied. Films were produced by sputtering multilayers of Cr and Pt onto silicon nitride coated silicon substrates. The as-deposited films are nonmagnetic. An anneal at ∼800 °C results in ferrimagnetic behavior with a perpendicular easy-axis. X-ray diffraction and transmission electron microscopy (TEM) measurements show that (111) CrPt3 is the only crystalline phase present after annealing. Rocking curves with a full width at half maximum as low as 1.8° indicate good crystallographic orientation. Magnetic properties of the films vary with composition, annealing temperature and time, layer thickness, and sputtering conditions. The films exhibit large coercivities, Hc, that can be tuned in the range 1500–8000 Oe. Saturation magnetization, Ms, is typically 150–200 emu/cc. Squarenesses, S, as high as 0.99 have been found. A uniaxial magnetic anisotropy constant, Ku, of up to 8×106erg/cc was achieved. TEM micrographs show a 35 nm average g...

SmCo thin films were grown onto highly oriented Cr/Ag/Si templates of various orientations and their properties compared to those of SmCo/Cr/glass thin film structures. No conclusive evidence of local crystalline order in SmCo films was observed by microscopy techniques. However, in-plane uniaxial magnetic anisotropy was observed for SmCo films grown onto Si(111) and (110) templates, indicating interfacial effects, while no anisotropy was observed for SmCo on Si(100). It is hypothesized that epitaxial growth of SmCo takes place on Cr(112) surfaces, but local crystalline order disappears with increasing SmCo thickness. Uniaxial SmCo films on Si(110) exhibit magnetic properties superior to those of SmCo on other Si templates. Process optimization could lead to SmCo media largely improved with respect to current SmCo films on glass.

Highly oriented NiFe thin films have been produced via sputter deposition on HF etched Si substrates. Cu and Ag are used as underlayers to induce the epitaxial growth of NiFe films. The orientation relationships between NiFe, Cu, Ag, and Si have been determined by x-ray diffraction measurements and transmission electron microscopy. Magnetic properties have also been characterized.

Crystallographic textures in a CoCrPtTa/Cr/NiAl multilayer magnetic recording media were studied by electron diffraction. It was found that texture quality evolves through the thickness of the films. A large improvement of texture quality was discovered at the interface of the Cr and NiAl layers. Surprisingly, there remains a portion of randomly oriented grains in the CoCrPtTa layer, in addition to the anticipated grains of [1010] texture. The texture quality of the CoCrPtTa layer remains similar to that of the underlying Cr layer.

CoCrPt/Ti/Ag films with the easy axes of the hexagonal-closed-pack Co grains perpendicular to the film plane were epitaxially grown on HF-etched Si(111) single crystal substrates by rf sputter deposition. The orientation relationship was determined by x-ray pole figure measurements and transmission electron microscopy to be CoCrPt(0001)[1010]∥Ti(0001)[1010]∥Ag(111)[112]∥Si(111)[112]. The magnetic properties of the CoCrPt films were greatly improved by introducing these single crystal templates. Rocking curve measurement showed a greatly improved c-axis orientation of the cobalt alloy. Highly oriented, high coercivity properties for perpendicular recording have been obtained.

Unicrystal Co–alloy/Cr/Ag films, which exhibit a single, in-plane easy axis orientation, were epitaxially grown on hydrofluoric acid etched Si(110) single crystal substrates by sputter deposition for the purpose of the systematic study of Co–alloy magnetocrystalline anisotropy. The orientation relationship was studied by x-ray θ/2θ diffraction, pole figure φ scan, and transmission electron microscopy, and it was determined to be Co(1010)[0001]‖Cr(112)[110]‖Ag(110)[001]‖Si(110)[001]. The φ scan also showed two twin-related orientations of Cr grains. The easy axis hysteresis loops had a square shape, while the hard axis loops showed zero openness. The uniaxial anisotropy constants K1 and K2 of the unicrystal Co and CoCrTa films were determined from torque and hard axis hysteresis loop measurements.

In this study, the effects of CrMn/NiAl and Cr/NiAl underlayers on microstructure and magnetic properties of CoCrPt magnetic layers are compared. CrMn intermediate layers were found to induce better in-plane texture and magnetic properties in CoCrPt films than Cr. Significant improvement in magnetic properties was achieved by post-deposition rapid thermal annealing (RTA). The anisotropy did not decrease much while grain isolation in the CoCrPt layer was achieved by using RTA.

A comprehensive review and state of the art in the field of surface, interface, and thin-film magnetism is presented. New growth techniques which produce atomically engineered novel materials, special characterization techniques to measure magnetic properties of low-dimensional systems, and computational advances which allow large complex calculations have together stimulated the current activity in this field and opened new opportunities for research. The current status and issues in the area of material growth techniques and physical properties, characterization methods, and theoretical methods and ideas are reviewed. A fundamental understanding of surface, interface, and thin-film magnetism is of importance to many applications in magnetics technology, which is also surveyed. Questions of fundamental and technological interest that offer opportunities for exciting future research are identified.

Chemical sensors based upon regioregular polythiophene thin-film transistors (TFT) are studied for their chemical sensing properties to volatile organic compound vapors. The sensing properties are found to be highly dependent upon the TFT operating conditions. As the applied gate voltage is varied the source-drain current response can differ both in sign and magnitude for the same analyte. This implies that multiple sensing mechanisms co-exist. Here, we propose that the two main sensing mechanisms are mainly due to a dipole interaction effect, which occurs inside the crystallites and yields a positive response, and a grain boundary (GB) effect, which yields a negative response.

A CoCrTa intermediate layer was added between a CoCrPt recording layer and a NiAl underlayer. CoCrPt (1010) texture improves and the in-plane coercivity increases using this medium structure. The effects of substrate bias on film texture and coercivity were studied. Pt concentration and lattice constant for CoCrPt were also characterized as functions of the bias voltage.

An improved CoCrPt thin film medium for longitudinal magnetic recording which has a coercivity significantly greater than prior CoCrPt thin film media was investigated. A CrMn alloy underlayer was used, instead of the conventional Cr underlayer. A coercivity value of 4280 Oe was easily reached in a CoCrPt film on a 50 nm thick CrMn underlayer as compared to 2810 Oe with a pure Cr underlayer. It was found that the coercivity increase due to the Mn addition was realized if the substrates were preheated before the sputtering. Grain boundary interdiffusion of Mn from the underlayer to the magnetic layer may be the cause for the coercivity increase.

Ultra-thin Co/Cr films were fabricated by RF diode sputtering. The highly exchange coupled Co grains were successfully isolated by post deposition processing. The microstructure was studied with TEM and a very small physical grain size was observed. The measurement of /spl Delta/M curves showed that the grain to grain interaction changed from positive to negative. Time dependent magnetic measurements showed significant thermal decay effects. It was also found that the use of CrMn underlayers instead of pure Cr further isolated the Co grains.

This work presents the fabrication and demonstration of an electroless gold plated CMOS-MEMS chemresistor array sensor for selective detection of volatile organic compounds, with conductive polythiophene polymer used as an active sensing material. Chemresistor electrode fabrication involves post-CMOS etching and electroless plating steps. An electroless gold plating process selectively deposits gold onto the CMOS aluminum electrodes to provide ohmic contact to the polymer layer. Electroless gold techniques are optimized to provide for a sub-micron vertical gap between the chemresistor electrodes. Polymer solutions are then deposited onto electrodes using drop-on-demand inkjet printing. Measured device response to methanol, acetone, and acetonitrile vapors demonstrates feasibility.

Regioregular polythiophene-based conductive copolymers with highly crystalline nanostructures are shown to hold considerable promise as the active layer in volatile organic compound (VOC) chemresistor sensors. While the regioregular polythiophene polymer chain provides a charge conduction path, its chemical sensing selectivity and sensitivity can be altered either by incorporating a second polymer to form a block copolymer or by making a random copolymer of polythiophene with different alkyl side chains. The copolymers were exposed to a variety of VOC vapors, and the electrical conductivity of these copolymers increased or decreased depending upon the polymer composition and the specific analytes. Measurements were made at room temperature, and the responses were found to be fast and appeared to be completely reversible. Using various copolymers of polythiophene in a sensor array can provide much better discrimination to various analytes than existing solid state sensors. Our data strongly indicate that several sensing mechanisms are at play simultaneously, and we briefly discuss some of them.

Low polydispersity regioregular polythiophenes with number average molecular weights ranging from 2 to 13 kDa were cast under the same conditions from solution to form a series of field effect transistors (FETs). Tapping mode AFM and grazing incidence small-angle X-ray scattering revealed that in all cases the polymers formed regular nanofibrillar morphologies with the width of nanofibrils proportional to the weight average contour length of polymer chains, indicating that conjugated backbones were oriented perpendicular to the nanofibril axes. FET charge carrier mobilities exhibited exponential dependence on nanofibril width, pointing to the decisive role of extended conjugated pathways in charge transport.

B2 ordered FeAl films with a small, uniform grain size have been produced by rf diode sputter deposition on glass substrates. CoCrPt films grown on FeAl underlayers were found to have the (1010) lamellar texture. The in-plane coercivities (Hc) of the CoCrPt/FeAl films are comparable to those of the CoCrPt/Cr films and they can be further improved by inserting a thin Cr intermediate layer between the CoCrPt and the FeAl layers. By employing a MgO seed layer or a (002) textured Cr seed layer, (001) textured FeAl can be obtained. However, the (001) FeAl underlayer only induces a weak (1120) textured CoCrPt. Thus no improvement in Hc over those produced on unseeded FeAl underlayers was observed.

Ag thin films were sputter deposited on hydrofluoric acid-etched Si(001) single crystal substrates and employed as templates for the epitaxial growth of Cr(001) films and consequently bicrystal CoCrTa(1120) films. The orientation relationship was determined to be bicrystal CoCrTa on Cr(001)[100]‖Ag(001)[110]‖Si(001)[110]. X-ray diffraction analysis showed only strong Ag(002) peaks throughout the Ag film thickness range of 50–1500 A. Atomic force microscopy showed that almost continuous Ag films can be achieved in the thickness range of 500–1000 A, which result in the highest coercivities in CoCrTa films whose magnetic properties were found to vary with the Ag template thickness and surface morphology. The periodic in-plane angular variation of magnetic properties and torque curves with a four-fold symmetry were confirmed in the bicrystal CoCrTa films.

The angular dependence of the remanent magnetic properties of uniaxially in-plane oriented barium ferrite films were found to deviate significantly from the Stoner-Wohlfarth (SW) coherent rotation model. The in-plane torque and the rotational hysteresis were studied in both aligned and randomly oriented films. They were found to be different from that calculated from the SW coherent rotation model, and suggested incoherent rotation of magnetization during the switching process. Incoherent rotation was found to be dependent on grain size and intergranular interactions.

The effect of different seed layers on the magnetoresistive (MR) properties of NiFe films has been investigated. Significant improvements can be observed and explained. By choosing seed layers that vary from conducting to insulating and from amorphous to crystalline the role of the NiFe crystalline texture and current shunting via the seed layer on the MR ratio is observed.

We have developed and synthesized highly conductive regioregular poly(3-alkylthiophene) (rr-PAT) derivatives for use in sensor arrays on a chip. Poly(3-alkylthiophene)s are ideally suited for this application because of their excellent electrical properties, solution processability and our ability to modify their chemical structure. Here, we synthesized rr-PATs that have different side chains and different end groups. The polymers were ink-jetted onto ChemFET devices on a chip and their chemical sensing properties were tested to a variety of volatile organic compounds (VOCs). The sensors demonstrated ppm level sensitivity and selectivity to all VOCs tested, including both polar and non-polar compounds.

A novel electrooptic beam deflector is reported based on ferroelectric domain inversion extending through the thickness of a Z-cut LiTaO/sub 3/ wafer. The selective domain inversion is achieved by electric-field poling assisted by proton exchange, rather than proton exchange followed by rapid thermal annealing. The deflection sensitivity of the device was measured to be 5.0 mrad/KV. This is 93% of the theoretical value for this geometry, and a significant improvement over the value of 80% of theoretical previously reported for a waveguide deflector. This improvement is attributed to the new domain inversion process. No degradation of deflection sensitivity is observed up to the frequency of 300 KHz, which is then limited by the response time of detectors.

The microstructure and in‐plane magnetic properties of Co72Cr10Pt18/NiAl thin films sputter deposited on (001) single crystal MgO substrates have been investigated. The orientation relationship between the NiAl underlayer and the MgO substrate is determined to be [001](100)NiAl//[001](110)MgO. The CoCrPt films grow in a fibrous manner on the (001) NiAl underlayer and the orientation relationship between the two layers is determined to be [1011]CoCrPt//[001]NiAl, and (1210)CoCrPt//(100)NiAl (variant 1), or (1210)CoCrPt//(010)NiAl (variant 2). The CoCrPt film has two sets of in‐plane magnetization easy axes. The major easy axes are along the MgO[100] (i.e., NiAl[110]) and the MgO[010] (i.e., NiAl[110]) directions and the secondary easy axes are along the MgO[110] (i.e., NiAl[100]) and the [110] (i.e., NiAl[010]) directions.

FeN materials exhibiting high moment, low coercivity and small magnetostriction have previously been reported. Zr has been known to reduce the magnetostriction in other Fe alloys. The criteria for an ideal recording head pole material as well as shields for magnetoresistive sensors include high moment, low coercivity, high permeability, and zero magnetostriction. We present here the properties of 0.3 μm thick rf sputtered FeZrN films measured as a function of the N2 partial pressure. The films were deposited at a pressure of 3 mT using a Perkin Elmer sputtering system. The target was composed of Fe with Zr chips covering approximately 2% of the surface area. The easy axis and hard axis coercivities show minima of 1.8 and 0.6 Oe, respectively, at 7–10 % N2 partial pressure with a saturation magnetization of about 18 kG. The magnetic anisotropy field is approximately 5 Oe yielding a dc permeability of approximately 4000 along the hard axis. X‐ray data reveal a systematic change in the ratio of α–Fe and γ–Fe4 N; the amount of the γ–Fe4N phase increasing with increasing N2 partial pressure. The magnetostriction increases with increasing N2 content crossing zero at approximately 6%. The grain size, as probed by atomic force microscopy, is an increasing function of the N2 partial pressure; from a few nm for N2 partial pressures of 5% to being as large as 50 nm for a partial pressure of 15%. The surface roughness is about 1 nm.