Laser Zone Research Articles

Take off measurement of pico sliders on laser zone textured media

This paper describes the need for proper signal conditioning of an acoustic emission (AE) transducer output for contact detection with pico sliders. The key to signal conditioning involves the design and implementation of a filtering scheme to target the pico slider body vibration frequencies in the range of 1.25-2.0 MHz. Data, in the form of the frequency content of the AE output measured on two different types of laser zone textured disks and a mechanically textured disk, as a function of disk rotational velocity, is presented to illustrate the validity of the properly tuned AE signal for contact detection. The data also indicates dependence of take off characteristics on media texture.

Issues on high-speed laser zone texturing of magnetic disk substrates with improved quality

Important issues of laser zone texturing in manufacturing are discussed. We report practical strategies in terms of tooling and process control. We found that good bump height uniformity is achieved by operating in the most stable region where the effects of laser pulse energy fluctuation, disk thickness variation, and disk runout are minimized. By selecting optimum process parameters, a bump height standard deviation of less than 1.5% can be achieved.

Effects of temperature and humidity on stiction behavior of laser zone textured disk

This study is to investigate the effects of relative humidity and temperature on contact start stop (CSS) performance. Commercially available 95 mm thin film disks with the diamond like coating were used in this paper. Disks were lubricated with Z-Dol. The coefficient of stiction was used to monitor the interaction between the head and the laser zone texture disk surface during CSS. The experimental data were investigated on the disk surface at 8%, 80% relative humidity and 5/spl deg/C, 35/spl deg/C, 60/spl deg/C, respectively. It was found that the coefficient of stiction was well correlated with the lubricant film thickness and adsorbed water film thickness at the head/disk interface. For the Z-Dol lubricant on mechanical and laser zone texture disk, the coefficient of stiction of head/disk interface at 5/spl deg/C, 8%RH was less than that of the 35/spl deg/C, 80%RH. The coefficient of stiction for laser-zone-texture disks was smaller than that of the mechanical-zone-texture disks. From these results it can be seen that the lower coefficient of stiction and the longer lifetime of CSS test was obtained at optimum condition.

A Method for Laser Zone Texturing of Glass Based Magnetic Media Using Nd:Yag Lasers

AbstractLaser zone texturing of nickel-plated, aluminum based magnetic media has become a preferred method of providing a precisely controlled head landing zone. The Nd:YAG lasers used for this process are not suitable for directly texturing glass substrates. A novel method has been developed which allows the use of the existing Nd:YAG laser systems to zone texture glass based magnetic media.An amorphous sputtered film of a non-magnetic Ni alloy provides a texturing layer which absorbs the laser pulse and controllably forms regular, small protrusions. Optimization of the alloy composition results in small cone-shaped bumps. Laser power sensitivity exhibits a region of invariance for a range of film thickness. This behavior provides a wide margin for manufacture by reducing the effect of thickness variation on laser bump height.Disks fabricated using this form of laser zone texture exhibit excellent tribology performance. TEM images show the Ni alloy to be amorphous and featureless. The sputtered film does not influence the properties of the subsequently sputter deposited isotropic magnetic films.

Projected Advances in Laboratory Soft X-Ray Systems and Their Applications

Advances in x-ray laser plasma sources and zone plate optics since the early 1980s are reviewed. The improvements are projected into the early years of the 21st century and it is demonstrated that applications such as x-ray microscopy will become increasingly amenable to small scale laboratory systems.

Gradual laser zone texture for low flying height sliders

We measured the Acoustic Emission (AE) signals of the Head and Disk Interface (HDI) during slider seek operations using laser textured disks. We found that a gradual laser zone located outside the normal laser zone decreases the shock of landing in the CSS zone when the head flying height and laser bump height are comparable.

Projected Advances in Laboratory Soft X-Ray Systems and Their Applications

Advances in x-ray laser plasma sources and zone plate optics since the early 1980s are reviewed. The improvements are projected into the early years of the 21st century and it is demonstrated that applications such as x-ray microscopy will become increasingly amenable to small scale laboratory systems.

Laser zone texturing on glass and glass-ceramic substrates

A RF driven CO/sub 2/ laser is used to create laser bumps on glass and glass-ceramic substrates. The resulting bump height is found to be a function of laser parameters such as pulse width, spot size, and pulse energy. Composition, structure and chemical strengthening of the substrates also affect the laser bump topography. Laser bumps on glass-ceramic, non-strengthened glass, or strengthened glass substrates, all exhibit net volume gain. Possible mechanisms for the volume increase include density change due to glass quenched to a subcooled state and/or due to phase transition from the crystalline phase to the glass phase. Stress release may play a role in the case of chemically strengthened glass substrates. The tribological performance of laser texture on glass and glass-ceramic substrates again shows low stiction and low friction build-up.

Tribological performance on laser zone textured disks

A wear model, based on Archard's law (1953), has been used to correlate with the volume wear rate of laser texture bumps on magnetic recording disks. The experimental results agree very well with the predicted model, except during the running-in period. This method was used for the wear resistance evaluation of various overcoat composition quantitatively instead of qualitatively. Wear volume measurement for the laser texture bump is much easier than that for the mechanical textured disk.

Design of laser zone texture for low glide media

The design of laser zone texture on NiP/Aluminum substrates to create below-25 nm-glide-height media is described in this paper. A range of laser parameters such as beam size, pulse energy, and temporal pulse width of a pulsed Nd-YVO/sub 4/ laser are explored to reveal their relationship to the resulting bump topography. Depending on where the head contact is formed, four major categories of bump shapes are found to exist. The single-crater bump shape was selected to conduct the low glide texture design. Stiction and glide performance are shown to be in agreement with theoretical predictions, which constitute our major design guidelines. It is clearly demonstrated that with proper texture design below-25 nm-glide-height media with low stiction and minimal wear are readily achievable even in the landing zone with laser texture.

Laser zone texture on alternative substrate disks

A sealed, compact, and low power CO/sub 2/ pulsed laser is used to melt a focused microscopic area on an alternative glass ceramic substrate. By precisely controlling the laser power, pulse duration, pulse rate, and the disk movement, a well-refined array of bumps can be produced on the alternative substrate. The laser bump formation on the alternative substrate shows a positive-extending volume without any negative-extending volume. TEM electron diffraction shows a phase change from polycrystalline to amorphous in the melted area. In addition to the stress release, the domed bump formation could be doe to the volume expansion of newly formed amorphous phase. The CSS test results show that the supersmooth glass ceramic disk stiction can be reduced by one order of magnitude by applying laser zone texture. The transition zone width between laser texture and data zones can also be made as small as a few milli-inches to increase the recording area.

Texturation of YBaCuO by laser zone melting

Recent results concerning texturation of YBa2Cu3O7−δ by laserzone melting are presented. It is shown that a melted zone at 1070°C enables growth at quasi-equilibrium. Single domain samples several mm long from millimeter wires have been obtained. The residual 211 content is small and its size is also smaller than that obtained by the conventional MTG process.

Rapid solidification of high-T/sub c/ oxide superconductors by a laser zone melting method

The direct crystallization of the YBa/sub 2/Cu/sub 3/O/sub 7/ orthorhombic superconducting phase from the solution of the 123 composition has been realized by a rapid solidification using a laser zone melting method. This method is characterized by two processing parameters: the temperature gradient (G) and the growth rate (R). Under the higher G and R conditions, the nonequilibrium phase transformation occurred, and the direct crystallization of the orthorhombic phase from the melt of the 123 composition was realized. An as-grown solidification sample exhibited superconducting phase transition at 94 K, according to a magnetization measurement. The structure in which Y/sub 2/O/sub 3/ fine particles dispersed homogeneously was obtained in the lower R region. It is possible to use this structure as a long and narrow precursor for the melt process. By annealing at 1000 degrees C, the critical current density of the sample was 1.5*10/sup 4/ A/cm/sup 2/ at 77 K, 0 T, according to a magnetization measurement.

Infrared Laser-Assisted Zone Refining of Inorganic Materials

This paper presents purification and crystallization of inorganic materials by laser zone refining (LZR), i.e., floating zone melting assisted by a high power infrared laser. The LZR heating system was composed of a Nd: YAG laser as a heat source, an optical fiber for laser beam transmission, and a focusing system. To determine LZR purification capabilities, 5mm zinc rods were melted and Pb impurity segregation was observed after refining the zinc rods. For the crystallization test, green bodies of 0.2μm α-Al2O3 fine powder were fused, and optically transparent single crystals were obtained. The LZR technique was found to be useful in the refining of inorganic materials.

Preparation of Ferroelectric Films of LiNbO3 and SbSI by Artificial Epitaxy.

AbstractHighly–ordered, up to nearly–single–crystalline films of SbSI and LiNbO3 on amorphous substrates (oxidized silicon, fused quartz) were prepared by laser zone–melting recrystallization basing on principles of artificial epitaxy, or graphoepitaxy. Some conclusions are made about tentative orientation mechanism(s) in these processes.

Laser zone-melted Bi-Sr-Ca-Cu-O thick films

Directionally solidified superconducting Bi-Sr-Ca-Cu-O thick films have been fabricated by laser zone melting. Highly aligned grain structures were obtained. Films with no post-processing anneal showed Tc(R=0)=82 K and transport critical current densities Jc as high as 450 A/cm2 at 77 K and 5400 A/cm2 at 60 K. After annealing for 65 h at 850 °C, Tc increased to 85 K, and the best sample showed Jc =2200 A/cm2 at 77 K and 11 200 A/cm2 at 60 K.

Highly Textured Superconducting Bi2Sr2CaCu2Oy Crystals Prepared by Unidirectional Solidification Processing

AbstractUnidirectional solidification processing, including Floating Zone Melting, Vertical Bridgman, and Laser Zone Melting methods for making high Tc superconducting oxides has been investigated. The effects of processing parameters, growth rate (R) and temperature gradient (G), on texture, morphology, and structures of unidirectionally grown crystals were investigated. Two different crystallization mechanisms were recognized, one is non‐equilibrium phase transformation under high GR conditions, and the other is due to local equilibrium phase transformation under low GR conditions. Strongly aligned structures were obtained at high G/R ratios with low GR value. The interrelation between the superconducting characteristics and textured structure produced were also discussed.

TEMPERATURE FIELD CONTROL MODEL OF LASER CRYSTALLIZATION OF HYDROGENATED AMORPHOUS Si

During Ar+ laser scanning at low speeds, four kinds of crystallization zone appear on a-Si:H films deposited on quartz substrates. They are microcrystalline phase zone, solid phase zone, supercooled liquid phase zone and liquid phase laser zone, grown by liquid phase transverse epitaxies. The temperature field control model of laser crystallization of hydrogenated amorphous silicon has been proposed, by which the crystallization processes and their features can be explained.

Comparison of laser and radiofrequency dorsal root entry zone lesions in cats

Comparison of laser and radiofrequency dorsal root entry zone lesions in cats

The chemical origins of sers effects: a review of laser microzone damage

A review of microscopic and spectroscopic data for silver electrode surfaces exhibiting surface enhanced Raman scattering (SERS), indicates a correlation between the observation of SERS and laser surface damage. Composition and morphology within the laser zone differ from the remainder of the surface. Therefore, silver surface enhancement factors estimated from assumed coverage and roughness parameters for non-illuminated surface zones are generally unjustified. To facilitate further elucidation of SERS effects from silver electrodes, a classification of enhanced scattering systems is proposed: I. Carbonizable adsorbates; II-Carbon-overlayered surfaces; III. Non-carbonizable adsorbates; IV. Non-enhanced adsorbates, and V. Resonant adsorbates.