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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.

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.

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 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.

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.

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 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.

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.

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.

Hexagonal Barium Ferrite thin films with perpendicular anisotropy were successfully fabricated on the (111) surface of large lattice constant (LLC) garnet substrates using pulsed laser deposition. Oxygen pressure plays a crucial role in determining film growth characteristics. The film grown at 50 mTorr oxygen pressure has a clear hexagonal structure but is very weakly crystallized due to the lack of oxygen. Increasing the oxygen pressure enhances both crystallization and the in-plane c-axis oriented crystal growth, hence it reduces the perpendicular anisotropy. The optimum pressure is about 180 mTorr which gives a crystallized film with predominantly perpendicular c-axis orientation. The sensitive dependence of film structure on processing gas pressure shown in this work is important in controlling film properties such as anisotropy and grain size for different applications.

The effects of record spacing on trackedge noise are studied for CoCrTa and CoCrPt-CoCrTa media. Variations in record spacing (separation from magnetic media to write head pole tips) are accurately achieved by using an identical set of disks for each type of media, with different overcoat thicknesses. Trackedge noise is characterized using track profiles of the media noise. An integrated spectral technique is used to measure media noise, and the effects of the different playback spacings (separation from magnetic media to read head pole tips or read element) are removed by dividing the spectral playback loss factor from the media noise spectra. Track profiles were performed at three linear record densities for each record spacing. For both media, on-track noise and trackedge noise are found to decrease with reduced record spacing, and the amount of decrease is found to be record density dependent. However, the trackedge noise did not decrease as dramatically as the on-track noise with reduced record spacing.

Sputter-deposited NiAl underlayers can induce better in-plane c-axis textures in the overlying CoCrPt films and have a smaller grain size than Cr underlayers. However, it is found that the CoCrPt/NiAl films on glass substrates have on lower coercivity values than the CoCrPt/Cr films. A scheme which inserts a Cr intermediate layer, about 2.5 nm thick, between the CoCrPt and NiAl layers is found to greatly improve the in-plane magnetic properties of the CoCrPt/NiAl films. The existing (10.

The magnetic properties and recording performance of multilayer CoCrTa thin film media with Cr or Ag interlayers are investigated. It is found that the coercivities and coercivity squareness of the films with Ag interlayers could be higher than that of the films with Cr interlayers. Recording tests show that the disks with Ag interlayers are noisier than the disks without an interlayer and the disks with a Cr interlayer. It is proposed that the increase in media noise when Ag was used as an interlayer is due to the RKKY coupling among magnetic grains through Ag.

In this work, interdiffusion and grain isolation in Co/Cr films have been investigated by studying the dependence of the magnetic properties on the substrate preheating temperature as well as on post-deposition annealing processes. By choosing pure Co instead of a Co-alloy, the possibility of grain isolation caused by the segregation of solute atoms from within the magnetic layer has been eliminated. It is found that both post-deposition thermal annealing and substrate preheating can effectively increase the isolation of the Co grains. >

In this work, the hysteretic properties and remanence curves of double-layer CoCrTa thin films with various interlayers (Al, Cu, Ag, and Cr) are investigated. It is found that the double-layer CoCrTa films with Cu or Ag interlayers have narrower switching field distributions but similar high coercivities, compared with the films with Cr interlayers. To understand the effects of interlayers on the magnetic properties, the crystallography of these multilayer thin films are studied. The results from this work show that Ag and Cu are strong candidates as interlayer materials in multilayer magnetic-recording media. >

A laser Doppler interferometric method using synchronous detection to measure the magnetostriction of soft magnetic films is described. The instrument measures 2 AA magnetostrictive deflections of Permalloy films on 500 mu m silicon substrates. Saturation magnetostriction of 10/sup -9/ can be measured for 1000 nm films on 100 mu m Si substrates. The ultimate resolution of the interferometer is 0.1 AA as demonstrated using piezoelectrically-driven mirrors. >

Crystallographic texture and lattice spacings of bias sputtered CoCrTa/Cr and Co/Cr thin films have been studied by X-ray diffraction. While only an insignificant change in the Co lattice spacing for the Co/Cr films was observed as the substrate bias voltage was increased, the increase in the CoCrTa lattice spacing for the CoCrTa/Cr films was substantial. The CoCrTa films showed nearly unchanged lattice spacings after a vacuum annealing for film stress release. The lattice increase appeared to be linearly proportional to the Ta content in the CoCrTa film. This implies that the Ta atoms tend to substitute randomly onto the hexagonal sites within the CoCrTa crystal grains, and that very little, if any of the Ta segregates to the grain boundaries. >

The magnetic properties and microstructural characteristics of CoNiCr/Cr films with thin Cr underlayers prepared on both single-crystal Si and glass substrates are discussed. It is found that [200] crystallographic texture is easily obtained for Cr films prepared on Si at room temperature. Substrate bias during the Cr deposition, however, changes the Cr [200] texture to [110]. Substrate bias during the CoNiCr deposition degrades the texture of the Cr underlayer. >

Multilayer magnetic recording thin-film media have attracted much attention because of their high signal-to-noise ratios. The authors investigated the crystallographic texture of the interlayer and the effects of the interlayer on the magnetic properties. It was found that: (1) when deposited at room temperature, the Cr interlayer has [110] texture, the same as the texture of the Cr underlayer; (2) when deposited at elevated temperatures, the Cr interlayer may have a different texture than that of the underlayer; (3) the Cr interlayer (only 25 AA thick) can either increase H/sub c/ or reduce S*, depending on the thickness of the CoCrTa layer; and (4) the substrate temperature affects H/sub c/ and S* dramatically. >

The effects of substrate temperature on CoCrTa/Cr thin films were investigated by depositing CoCrTa films on Cr underlayers/sur with various crystallographic textures at both room temperature and elevated temperature. Contrary to the notion that crystallographic textures of [1120] and [1100] are required to obtain high in-plane coercivity (H/sub c/) and low noise in Co/Cr based thin-film media, the present experimental results show that both H/sub c/ and Delta M depend more strongly on the sputter temperature of the magnetic layer than on its crystallographic texture. It was also found that the Delta M of [1101]/sub Co//[110]/sub Cr/ textured films is lower than that of the [1120]/sub Co//[200]/sub Cr /films with similar H/sub c/. This suggests that [1101]/sub Co//[110]/sub Cr /textured media might have better signal-to-noise properties. >

Track-edge noise was evaluated by means of spectrum analyzer measurements performed on isolated tracks, one recorded at 16 kfci and the other 40 kfci, on CoCrPt, CoNiPt, and CoCrTa media. The track-edge media noise correlated with intergranular exchange coupling and the initial erasure state of the media. This study of track-edge effects has confirmed the nature and existence of side-erase bands, located on either side of a recorded track for the three different thin-film media. Track-edge media noise was more noticeable for the 16 kfci tracks recorded on both previously AC- and DC-erased media. The track edges for the 40 kfci track recorded on previously DC-erased media proved to be regions of high noise which extended beyond the radial extent of the written track. >

This paper reports on Co{sub 62.5} Ni{sub 30}Cr{sub 7.5} thin films that were sputtered onto (100) and (110) Cr single crystals as well as polycrystalline Cr TEM folls. VSM measurements have revealed the existence of an anisotropy in the in-plane coercivity. This stems from the development of a crystallographic texture in the plane of the film. TEM investigations have found the presence of crystallographic variants in the direction of the hcp c-axis in the CoNiCr films deposited on (100) and (110) Cr surfaces. Lorentz microscopy studies have found relatively straight domain walls which lie parallel to the specific crystallographic directions. The direction of magnetization within each domain is along the c-axis.

The dependence of microstructure and magnetic properties of RF-sputtered thin films of Co-Ni-Pt deposited on NiP/Al and Cr/NiP/Al substrates was studied as a function of platinum composition, Ar pressure, and sputtering power. Transmission electron microscopy and electron and X-ray diffraction were utilized to determine the correlation between the observed coercivity, remanence squareness behavior, and microstructure. It has been found that in the case of films on NiP/Al substrates, the coercivity is controlled by the grain size, whereas it is dominated by the relative amount of the HCP and FCC cobalt phases for the films deposited on a 300-nm Cr underlayer. An increase in the Ar pressure leads to a further increase in coercivity for both substrates. This behavior was attributed to an increase in the grain size and a more favorable c-axis orientation of the HCP cobalt phase for Cr and NiP underlayers, respectively. >

The dependence of magnetic properties and microstructure of a sputtered thin film medium for high-density longitudinal recording on a Cr underlayer and circumferential substrate texture has been studied. The combined use of the underlayer and substrate texture induces circumferential anistropic magnetic properties in the medium. In the media without and with the underlayer on textured substrates, the dominant planes lying in the film surface are Co hcp {0002} and {01 1 1}, respectively. Grain boundary matching between the medium and the underlayer, as observed by cross-sectional transmission electron microscopy (TEM), indicates that the medium grows by replicating columnar grains in the underlayer. With this replication, grains in the medium with the underlayer are much larger than those in the medium without the underlayer. The circumferential anisotropy occurs only when the grain diameter of the medium is of the same physical size as the surface roughness and the grain boundaries are aligned by the substrate texture.