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FePt (10, 20, 40, and 60 nm) films were fabricated on four different single crystal substrates [MgO (001), KTaO3 (001), SrTiO3 (001), and LaAlO3 (001)], and the effects of lattice mismatch on the microstructure and magnetic properties of FePt films were systematically investigated. The X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) results showed that the different lattice mismatch between the substrates and FePt films resulted in the different crystallographic texture and microstructure of the FePt films. Under the tensile strain between the FePt and substrates (MgO, KTaO3, SrTiO3), the FePt films preferred to form L10 FePt (001) texture. The perpendicular anisotropy of the FePt films grown on MgO was larger than that grown on KTaO3 and SrTiO3. For the FePt films grown on the LaAlO3 substrate, both FePt (110) and (001) orientations were found, which indicated the presence of tensile and compressive strain, respectively. With the reduction of the lattice mismatch between the FePt (10 nm) and substrate from 5.8% (MgO) to 2.4% (KTaO3), and 0.1% (SrTiO3), the microstructure of the FePt films changed gradually from granular to continuous films (SEM and TEM results). The microstructure of the 10 nm FePt film grown on LaAlO3 substrate showed granular structure. [ABSTRACT FROM AUTHOR]

Multilayer exchange spring media were fabricated by subsequently reducing the deposition temperature of the FePt-C film from the bottom layer to the top layer. Magnetic anisotropy and coercivity of FePt-C film increased with the increasing of deposition temperature because the chemical ordering of L10 FePt improved with deposition temperature. A two-layer microstructure was observed in the multilayer samples with a closely-packed granular hard layer and an isolated granular overlayer consisting of the soft magnetic layers deposited at lower temperatures. The coercivity of the tri-layer media was reduced to 5.4 kOe, half of that of the hard single layer FePt-C (10.8 kOe). The thermal stability of the multilayer structure was maintained although some soft magnetic layers involved. [ABSTRACT FROM AUTHOR]

We reported the fabrication of (001) textured FePt–TiO2 exchange coupled composite (ECC) media including hard/soft bilayer and multilayer with well isolated columnar microstructures. The magnetic anisotropy of FePt–TiO2 was adjusted by applying various substrate bias during film deposition. The cross-sectional transmission electron microscopy images showed isolated granular microstructures in single hard layer, bilayer, and multilayer media. For the bilayer media, it was observed that both the coercivity and magnetization squareness of composite media decreased with increasing thickness of the soft layer. A soft layer with the thickness of 4 nm was more effective to significantly reduce the switching field and maintain a higher thermal stability factor than that of others. Incoherent switching behavior was observed as the soft layer thickness was increased to 6 nm. For multilayer media, it was found that the out-of-plane coercivity decreased to 6.5 kOe, which was close to half of that of the single hard layer. However, the thermal stability factor of the multilayer media slightly decreased compared with the single hard layer and bilayer media due to finite thickness. The results suggested a way to obtain the adjustable anisotropy for ECC media in high density magnetic recording application. [ABSTRACT FROM AUTHOR]

The effects of Ru underlayer on crystallographic structure, microstructures, and magnetic properties of Co72Pt28 films were investigated. It was observed that Ru deposition pressure played a more important role in determining the crystallographic texture compared to Ru thickness. Ru had a preferred (0002) texture when deposited at low Ar pressure and induced perpendicular magnetic anisotropy for Co72Pt28. However, at high Ar pressure, Ru (1010) and Ru (1011) peaks appeared that changed the easy axes of magnetization of Co72Pt28 film from out-of-plane to in-plane directions. With increasing thickness of Ru top layer in the dual-layer structure of Ru underlayer, coercivities increased due to increased magnetic anisotropy and reduced intergranular magnetic interaction. [ABSTRACT FROM AUTHOR]

L10 FePt–Ta2O5 films with (001) texture were synthesized by cosputtering FePt and Ta2O5 targets and in situ heated at 350 °C. The (001) preferred orientation was preserved even when doped with 20 vol % Ta2O5. The out-of-plane coercivity, Hc, increased from 6.7 kOe (for pure FePt film) to 8.8 kOe when doped with 20 vol % Ta2O5. Further increase in the dopant content to 25 and 30 vol % caused Hc to decrease significantly to below 3 kOe. Well-isolated FePt grains of tall column structures were observed for the 12 nm thick FePt film when doped with 20 vol %. The loop slope parameter, α, of such FePt film approached 1. [ABSTRACT FROM AUTHOR]

The effects of interlayer coupling on switching field and magnetization reversal mechanism of Co72Pt28–SiO2(hard)/Co–SiO2(soft) exchange coupled media were investigated. The soft layer, with thickness less than the domain wall width, followed domain wall assisted switching mechanism for direct interlayer coupling between the hard and soft layers. It was effective in significantly reducing the switching field. The strength of interlayer coupling between the hard and soft layers was controlled by inserting the Pt intermediate layer between them. The reduced interlayer coupling led to independent switching of the hard and the soft layer and was ineffective in reducing the switching field. [ABSTRACT FROM AUTHOR]

The microstructure and magnetic properties of granular FePt-SiNx-C films were modified by introducing an MgO nucleation layer grown on the TiN intermediate layer. It was found that the deposition of an ultra-thin MgO nucleation layer could reduce the FePt grain size, narrow grain size distribution and improve grain isolation by creating more nucleation sites. When MgO nucleation layer thickness varied from 0 to 0.36 nm, FePt grain size was reduced from 8.51 nm to 7.18 nm and the standard deviation of the grain size distribution was narrowed from 2.16 nm to 1.51 nm. Good L10 (001) texture was maintained and large out-of-plane coercivity (27.5 kOe) was obtained at the MgO thickness of 0.36 nm. Meanwhile, \Delta \theta50 of FePt (001) peak decreased from 7.1^\circ to 6.4^\circ, indicating the improved easy axis distribution of FePt grains. However, with the further increase of the MgO nucleation layer thickness, MgO nuclei developed into a continuous layer, FePt (111) orientation appeared and the perpendicular magnetic anisotropy was deteriorated. [ABSTRACT FROM AUTHOR]

The effects of a TiN intermediate layer on the microstructure and magnetic properties of the FePt films were investigated. It was found that the TiN layer could effectively block the diffusion of Cr into the FePt film. The good epitaxial relationships among these layers were revealed from the transmission electron microscopy (TEM) results. With introducing TiN intermediate layer the chemical ordering and magnetic properties of FePt films significantly improved. The FePt film with 5 nm TiN exhibited a high perpendicular coercivity of 13.7 kOe and a low in-plane coercivity of 0.24 kOe, resulting from the combined contribution of TiN (200) orientation, TiN layer roughness and the effective block of Cr diffusion. Moreover, with doping C into the FePt-SiNx films, the out-of-plane coercivity increased due to the decrease of the exchange coupling, the grain size of FePt films decreased, and well-separated FePt grains and uniform size were formed. By optimizing the sputtering process, the [FePt (4 nm)-SiNx 40 vol\cdot\\%]- 20 vol\cdot\\% C (001) film with coercivity higher than 21.5 kOe, a single layer structure, and small FePt grain size of 5.6 nm in average diameter was obtained, which are suitable for ultrahigh density perpendicular recording. [ABSTRACT FROM AUTHOR]

The investigation on the lattice relaxation of FePt/TiN heteroepitaxial film was conducted by means of the thickness-dependent evolution of microstructure and magnetic properties. The critical thickness of FePt epitaxial growth on TiN was determined to be around 10 nm based on the lattice constant simulation according to equilibrium theory, which was consistent with the experimental value obtained from cross-sectional transmission electron microscope (TEM) measurements. Using high-resolution TEM images, the lattice relaxation mechanism of the FePt layer was clearly explained via the formation of edge dislocations at the critical thickness and the ensuing tilt of {1 1 1} lattice planes towards the film normal direction. It is found that the lattice relaxation caused the misorientation of the easy axes, and therefore in-plane magnetization increased and perpendicular anisotropy deteriorated with FePt thickness increasing from 10 to 40 nm. [ABSTRACT FROM AUTHOR]

A maskless technique for the fabrication of U-shaped microstructure arrays on the surface of photosensitive glass by femtosecond laser-induced modification is developed. This technique is followed by heat treatment to crystallize the modified area, and the specimen is then placed in acid solution for chemical etching. The surface roughness of the microstructures is further improved by a secondary annealing process. The fabricated photosensitive glass is used as a mold template, and replicated plano-convex cylindrical arrays by UV-replica are also presented. The focusing ability of the microlens arrays on the glass mold and replicate is demonstrated. [ABSTRACT FROM AUTHOR]

Sputtered Ru and Ru-C films 5 nm thick are employed in the Cu/barrier/SiO2/Si system, and their performances as the diffusion barrier as well as the seed layer for direct Cu electroplating are investigated in parallel. Based on the sheet resistance measurement and energy dispersive X-ray line profiles, the 5 nm Ru-C film can retard the diffusion of Cu after a prolonged (30 mm) annealing up to 700°C, while the Ru film is an effective barrier up to only 400°C. Direct electroplating of Cu is successfully carried out on both Ru and Ru-C films, which proves that Ru-C is a Cu seed layer in addition to being a robust diffusion barrier. The microstructural characteristics of ultrathin Ru and Ru-C films are also examined, indicating that the superior barrier performance of the 5 nm Ru-C film is associated with its inferior crystallinity and resistance to agglomeration at elevated temperatures. [ABSTRACT FROM AUTHOR]

The FePt:C films with different volume fractions of carbon were epitaxially grown on the CrRu(200) underlayer with Pt and MgO intermediate layers. The magnetic properties and microstructure of these FePt:C films were investigated. The FePt:C films grown on Pt intermediate layer consisted of a continuous layer of FePt, with overlying granular FePt grains. The FePt:C films grown on MgO intermediate layer consisted of a granular FePt:C layer with overlying granular grains. The formation of the overlying granular FePt grains was attributed to carbon diffusion to the surface, which resulted in the second nucleation of FePt. The different interface energy and surface energy of FePt on Pt and MgO intermediate layers caused the formation of initial continuous FePt layer on Pt intermediate layer and initial granular FePt layers on MgO intermediate layer. The out-of-plane coercivity measured at room temperature increased from 10.2 to 19 kOe when C concentrations increased from 0 to 15%. Further increasing the C contents to 20% and 25% caused the decrease of coercivity to 17.2 and 14.8 kOe, respectively. The coercivity of the exchange coupling assisted FePt:C perpendicular media was indeed substantially reduced. [ABSTRACT FROM AUTHOR]

Ultrathin Ru-N and Ru-Ta-N films (~ 15 nm in thickness) deposited by reactive sputtering are applied as a diffusion barrier in the Cu/barrier/SiO2/Si systems. After film deposition, the samples are tested before and after annealing at 200-900°C in vacuum for 30 mm. The sheet resistance examined by four-point probe appraises that the Ru-Ta-N barrier would not fail until annealing at 900°C, as compared to Ru-N, which fails after annealing at 600°C. The depth distribution of elements examined by Auger electron spectroscopy confirms different degrees of Cu diffusion into underlayers for the two systems after annealing at 600°C. Also, the cross-sectional microstructures of the Cu/barrier/SiO2/Si samples analyzed by transmission electron microscopy, the crystallinity of barrier films examined by grazing incident angle X-ray diffraction, and the chemical state of barrier characterized by X-ray photoelectron spectroscope might explain the difference in barrier performance for the ultrathin Ru-N and Ru-Ta-N films in the Cu/barrier/SiO2/Si multilayered systems. [ABSTRACT FROM AUTHOR]

In this work, the microstructure and oxidation resistance of pure Cu, Cu(0.2 at.% Zr) and Cu(2.5 at.% Zr) alloy films deposited on SiO2/Si by sputtering were explored. Upon annealing, the Zr additives diffused to the free surface and reacted with the residual oxygen in the vacuum system. An additional ZrO2 layer formed and covered the Cu(2.5 at.% Zr) film surface after annealing at 700 °C for 30 min. Simultaneously, of the three films, the Cu(2.5 at.% Zr) film exhibited the highest degree of Cu(111) preferred orientation and the lowest degree of void growth upon annealing. Additionally, the Cu(2.5 at.% Zr) film pre-annealed at 700 °C showed a superior oxidation resistance when annealed at 200 °C in air for 15 min. Microstructure and oxidation resistance of Cu(Zr) alloy films were clearly affected by the ZrO2 layer formed via the segregation of Zr additives, and the connection is discussed. [ABSTRACT FROM AUTHOR]

Polymer memory devices using poly(N-vinylcarbazole) (PVK) as the active layer, incorporated with various weight ratios (0, 0.083, and 0.2) of dodecanethiol capped gold nanoparticles (Au NPs), are investigated. Electrical bistability is demonstrated for all three PVK-based devices, regardless of Au-NP ratios. However, current fluctuation is observed during stress test for both zero (PVK-only) and Au NPs:PVK=0.2:1 devices, while good current stability is obtained for the Au NPs:PVK=0.083:1 device. Capacitance-frequency (C-f) curves present the comparable negative capacitance feature for all three devices in both high-conductivity (“on”) state and low-conductivity (“off”) state, indicating that the carrier transport is dominated by the PVK matrix. However, minor differences in the C-f curves are dependent on the weight ratios of Au NPs, and the connection is discussed. [ABSTRACT FROM AUTHOR]

The microstructures and magnetic properties of FePt films grown at 350 °C on glass substrates with MgO (200) intermediate layer and CrRu (200) underlayer were investigated. The film with 1 nm MgO intermediate layer showed higher degree of chemical ordering than that with 4 nm MgO layer due to the compression of the lattice constant of 1 nm MgO intermediate layer along the [100] direction. Isolated FePt particles were formed when nominal thickness of FePt was 4 nm. The room temperature coercivity of isolated FePt particles with 1 nm MgO intermediate layer was as high as 12 kOe, significantly larger than that with 4 nm MgO intermediate layer (6.3 kOe). [ABSTRACT FROM AUTHOR]

The effect of the CrRu-SiOx underlayer with different doping concentrations and the thickness of the CrRu underlayer on the microstructure and magnetic properties of FePt-C films were investigated. FePt films exhibited L10 (001) texture at various SiOx doping concentrations. The coercivities were as large as 28 kOe and the slope of M-H loop at coercivity was approximately equal to 1, suggesting that FePt grains were well exchange decoupled. Grain size was only slightly reduced after introducing the CrRu-SiOx underlayer. But the contact angle between the FePt grains and the MgO intermediate layer around 135° indicated the a MgO intermediate layer was not favored for smaller grains to obtain good L10 (001) texture. X-ray photoelectron spectroscopy in-depth profile showed that Si diffused into a whole FePt-C layer and C diffused to the film surface. [ABSTRACT FROM AUTHOR]