Table of contents

It has been common practice to apply a surface texture to the disk surface in a hard disk drive in order to minimize the stiction force caused by the contact of the extremely smooth surfaces of the head slider and disk. The surface of head sliders is usually made as smooth as possible without any purposely formed texture. In this work, a texture on the hard-disk slider surface was formed by ion-beam etching as a result of the different etching rates among the different phases composing the material of the hard-disk slider. By this method, an island-type texture can be formed on the air-bearing surface of the hard-disk slider. The relation between the texturing condition, the slider material and the shape of the obtained texture is discussed. The texture area ratio was 6-36%, and the diameter of the island was in the range of 0.3-4 µm. The texture area ratio and island diameter could be changed by changing the composition of head slider material. The height of island could be linearly controlled from 3-20 nm with an accuracy of ±1 nm by changing the dose of the ion beam. It is concluded that ion-beam texturing is a promising method for producing texture on the slider surface, with the advantage of simple processing.

New models that describe gas flow behaviour in microtubes are presented. To avoid time-consuming calculations in solving the integral equation which is obtained from the microscopic point of view, the high-order slip-flow boundary condition is utilized to correct the gas flow in such a micron or submicron spacing. The proposed model can be applied to arbitrary Knudsen number conditions under the assumption that the bulk flow velocity is negligible compared with the sonic velocity of the gas. The analytical solution of the pressure distribution for the first-order slip-flow model is obtained. The results show that the first-order slip-flow model is in good agreement with this model. The nonlinear pressure distribution is due to gas compressibility. The dominant mechanism influencing the nonlinear pressure distribution comes from the rarefaction of gas and the inlet pressure. The rarefaction effect increases the pressure drop at the inlet region of the channel and decreases the pressure drop at the exit region of the channel. The decrease of inverse Knudsen number changes the pressure distribution from concave to almost linear and increases the mass flow.

A new atomic force microscope (AFM) for direct comparison measurements of step heights and crystalline lattice spacing has been developed. The AFM is equipped with a cantilever with a lead zirconate titanate (PZT) thin film sensor, a reference crystal technique with a scanning tunnelling microscope (STM) for step height measurement, high accuracy mechanisms, and an interferometer. A mono-atomic step on a surface of sapphire (0001) has been measured to show the performance of the AFM. The measured step height of the mono-atomic step calibrated by the interferometer in real time was 0.21±0.07 nm (1σ) and from the known lattice constant of graphite of 0.246 nm, a step height of 0.19±0.05 nm (1σ) can be derived for the sapphire sample, both of which agree with the known value of a single step of 0.22 nm.

The etching characteristics of CVD (chemical vapour deposition) diamond films processed with an ECR (electron cyclotron resonance) oxygen plasma are investigated. The etching rate increases linearly with increasing microwave power in the range from 100 to 300 W. For any value of microwave power, the etching rate first increases with increasing gas flow rate, reaches a maximum rate at a gas flow rate of 3 sccm (standard cc min^-1), and then decreases gradually with further increase in the gas flow rate. The etching rate increases linearly with increasing negative bias voltage in the range from 0 to -600 V. The etching rate for 100 and 300 W of microwave power and a negative bias of -600 V is 17 and three times greater, respectively, than that for 0 V bias. The surface roughness increases with increasing microwave power in the range from 0 to 300 W. The surface roughness before etching is eight times greater than that obtained after plasma etching with 300 W of microwave power. The Raman spectrum of a CVD diamond film after oxygen plasma etching for 1 h shows not only a diamond (sp³ bonding) peak at 1333 cm^-1, but also a broad non-diamond (sp² bonding) peak around 1500 cm^-1. However, as the etching time increases, the broad non-diamond peak around 1500 cm^-1 disappears.

A method for direct in situ thickness measurements of ultra-thin soft polymer films is presented in which an atomic force microscope (AFM) tip is used to create a furrow in the film, whereby the thickness is determined by scanning the sample across the furrow with the AFM. The sample does not need to be moved since the scratching and the measurements are performed with the same apparatus. This `furrow method' is applied to layer-by-layer polymer/polyelectrolyte ultra-thin films onto hydrophilic glass and silicon wafer substrates. This procedure is made possible because the polymeric film is less stiff than the substrates and the silicon tip. Results for 10-12-bilayer films are comparable to those obtained from profilometry, whose accuracy is only reasonable for films with more than ten bilayers. Taken together, the AFM and profilometer results show that film thickness increases linearly with the number of bilayers. Furthermore, the film thickness does not seem to depend on the substrate used but only on the number of bilayers deposited.

A precision micropositioning system with a high displacement resolution and wide motion range has been required for industrialized applications for a long time. This paper discusses the design and the characteristics of a new piezodriven precision micropositioning stage utilizing flexure hinges. Two-grade amplifying and a monolithic symmetrical mechanism are adopted in the design. An analytical model is presented and a series of formulae for the static and dynamic behaviour of the stage are derived. Based on the theoretical analysis, the optimum design schema is put forward. The experimental demonstration to study the performance of the stage is described, and the method for reducing nonlinearity errors is proposed. The experimental results are in close agreement with those predicted by the theoretical analysis.

In this paper, we report on atomic force microscopy (AFM) investigation of a self-assembled monolayer (SAM) system - octadecylphosphonic acid (OPA) deposited on mica. With the deposition methods employed in this work, the SAM presents a partial coverage, i.e., the OPA covers only a fraction of the mica surface and, therefore, some bare mica regions are observed. Using standard intermittent contact AFM (IC-AFM) techniques (with medium to high oscillation damping), the topographic profile of this system clearly shows the flat SAM on top of the mica surface. However, when a small oscillation damping mode is employed, the topographic profile is inverted, i.e., the mica regions appear higher than the surrounding OPA layer. AFM experiments, carried out to assess the origin of this effect, yield strong evidences that it is related to the presence of a water contamination layer on the bare mica regions only. A semi-quantitative model is utilized to understand the experimental results.

Nanoscale domain engineering in ferroelectric crystals is demonstrated down to a lateral domain size of 25 nm in diameter using scanning force microscopy (SFM). The various modes of SFM are used to measure both the internal polarization field and external stray field arising from bound surface charges in ferroelectric domains. From these measurements the effective three-dimensional arrangement of ferroelectric domains is reconstructed. Domain switching is initiated applying strong electric fields between the tip and counter electrode. The size of freshly nucleated domains is found to depend dramatically on the switching conditions, i.e. the applied electric field strength and switching time. Domains of less than 100 nm in diameter result for an electric field E_exp >50 kV cm^-1 applied for an ultra-short time period τ_exp <30 µs. Also, the coercive field of nanoscale ferroelectric domains in BaTiO₃ single crystals is found to measure 1.4 kV cm^-1, much more than the bulk value. Analysis of the transient response during domain switching shows that domain nucleation proceeds within less than 100 µs. With these tools we are able to record nanoscale hysteresis loops monitoring both the successful domain reversal and a well established material contrast between different ferroelectric structures with a resolution of better than 0.1%.

The aim of the paper is to demonstrate the successful operation of a combination of a scanning tunnelling microscope (STM), as a prominent representative of scanning probe microscopes (SPMs), with an x-ray interferometer (XRI). X-ray interferometry provides a means of calibrating nanometric displacement transducers and related instruments using silicon lattice parameters as secondary length standards. On the other hand, SPMs could be used to calibrate standards e.g. diffraction gratings for dimensional metrology. The extent of the measuring ranges covered by these instruments is wide, ranging from the diameters of atoms to dimensions of 100 µm. Some special instruments, so-called metrology SPMs, are calibrated against a laser interferometer and are affected by the laser interferometer's nonlinearity which is in the range of 1-2 nm. This uncertainty is a limit to the SPM and to the samples calibrated. Further improvement is necessary. If use is made of the high resolution of an x-ray interferometer when measuring the displacement of a sample under an SPM, a higher accuracy should be achievable and it should be possible to calibrate transfer standards with subnanometre accuracy. Here we report, for the first time, results of pitch measurements obtained for a structure on a sample, not of ideal shape but available for this experiment. The translation of the sample and the measurement of its profile were performed by a specially developed scanning XRI which uses the almost homogeneous silicon lattice spacing (Δd/d<10^-7) as a (secondary) length standard for subnanometre measurements (the so-called `Angstrom ruler').

We report on a new method to build suspended silicon nanowires in highly doped silicon films in silicon-on-insulator substrates. The beams are defined by high-resolution, low-energy electron-beam lithography using a two-layer positive electron resist. Micromachining techniques including dry and wet etching are applied to pattern the structures. We show first low-temperature measurements of these novel devices indicating electron-phonon interaction.

A tested, verified, and calibrated lithography simulator, based on cellular automata, is used to study phenomena, the effects of which are becoming more pronounced as the integrated circuits (ICs) are pushed deeper into the nanometre region. Lithography profiles developed on non-planar Si surfaces, where a step or a sloped line is present, were studied. Numerical experiments that elucidate effects such as the resist surface roughness on the developed profiles, as well as the effect of defects located into the resist bulk, in the presence of non-planar Si surfaces, are also presented. These effects are expected to be more pronounced as the integrated circuits are pushed deeper into the nanometre region.

Recently, our work on the measurement of Si(111) single atomic steps has prompted us to investigate the algorithm for the calculation of a one-sided step height. We compared the results of a two-point subtraction and a histogram technique under different conditions of surface tilt with respect to the measuring frame. By evaluating a simulated Si(111) atomic step, we found its calculated height could deviate from the true value as high as 2% due to a misalignment of the measuring axis and sample axis of 0.1°.

The adsorption behaviour of water-soluble negatively charged poly(ethylethylene-block-styrene sulfonic acid) on graphite surfaces has been investigated by dynamic scanning force microscopy in aqueous environments. Exploring the influence of added electrolytes, i.e. NaCl, on the aggregate structure was a further aim of this study. The obtained results were compared with prior experiments performed in air in order to investigate the influence of the drying effect on the adsorbed aggregate morphologies. Our results show that on graphite the drying process itself has no significant influence on the formation process of the different morphologies. A theoretical analysis of the adsorption of the micellar structures on hydrophobic substrates based on the experimental results is also presented.

In this study, the characteristics of an ultra-thin gas squeeze film are analysed using the modified molecular gas film lubrication (MMGL) equation with coupled roughness and rarefaction effects taken into consideration. A modified squeeze number (Σ) and modified plate aspect ratio (β) are proposed to estimate molecular gas film lubrication characteristics. Using Σ, β and a simple mapping method, the linearized MMGL problem can be reduced to the continuum gas film problem and the MGL characteristics can be exactly estimated if the pressure flow factors (ϕ_X^P,ϕ_Y^P) and the rarefaction coefficient (_P(D)) are known. The present models are computationally compact, and thus applicable to simulation of a microelectromechanical system.

High-performance actuation is always desirable in a dexterous high-precision manipulation system. In this paper, we first develop a single-degree-of-freedom piezoelectric translator composed of a piezoelectric stack, a monolithic leaf spring and a preload mechanism. The displacement resolution reached by this translator is better than 10 nm, while its natural frequency is over 2 kHz. Based on the developed piezoelectric translator, a micro-manipulator is then designed, which is capable of producing micro-motions in six degrees of freedom. The design characteristics and kinematics of this micro-manipulator are investigated. An effective kinematic model used for the real-time control is presented, and the operation performance of the micro-manipulator is discussed further.

The detection of hydroxyl-groups by chemical force microscopy is investigated in two contrasting solvents: water and hexadecane. Gold-coated cantilevers were chemically modified in a defined way by self-assembly monolayers (SAMs) formed by mercapto-undecanol. The samples employed consisted of ultraflat gold surfaces terminated by hydroxyl- and methyl-groups. Both surface terminations were present on the sample surface in a well-defined pattern obtained by micro-contact printing (µCP). High-resolution lateral force microscopy (LFM) was conducted in both solvents. These LFM measurements were complemented by measurements of the adhesion forces on the same substrates. In contrast to water, the empolyment of hexadecane, it enables specific detection of hydroxyl-groups and clear interpretation of the friction contrast.

Nanoscale science and technology is today mainly focused on the fabrication of nanodevices. Our approach makes use of lithography processes to build the desired nanostructures directly. The fabrication process involves an electron-beam lithography technique to define metallic microstructures onto which nanometre scale patterning is performed using an atomic force microscope (AFM) as a mechanical modification tool. Both direct material removal and AFM-assisted mask patterning are applied in order to achieve the smallest possible separation between electrode pairs. The sample preparation involves a polymer deposition process that results in conformal growth and in surface roughness comparable to that of the substrate. The results of the application of this technique show that the process is reproducible and exhibits a good operation control during the lithographic steps, both ensured by the imaging facilities of the AFM. The nanolithography technique has been used to fabricate nanogap electrodes to be used for molecular devices. The study reported here can be considered as a reliable starting point for the development of more complex nanodevices, such as single-electron transistors.

This paper presents the concept of dynamical hierarchies as a constructional and organizational principle in biomolecular materials design. Simple objects, characterized via a minimal set of explicit properties, self-organize into aggregates (higher-order objects) which show emergent properties (function) that are not explicitly encoded on the level of the individual chemical elements but are implicitly generated via the system dynamics.

Object aggregation may span various levels of complexity, which are linked by both, up- and downward causalities, forming a unique organizational element; a dynamical hierarchy. This organization of individual objects is characterized by multiple levels of constructional complexity accompanied by respective emergent properties and overall, stabilized by implicit control. This concept is well suited to design multicomponent chemical aggregates or chemical reaction networks with complex functionality.

We present the lattice molecular automaton (LMA) to simulate the generation of dynamical hierachies in chemical systems. This simulation tool encodes chemical objects (substrates, enzymes, products) as data structures storing their explicit properties as well as object-object communication data. These two attributes are accessed by an update functional driving the system dynamics.

We present LMA simulation results on dynamical hierarchies of structure and control in chemical reaction networks and discuss their implications for chemical information processing devices.