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We studied methods of estimating three-dimensional (3-D) tip structure using impulse response technique. We have proposed a 3-D tip estimation method using an infinite small diameter standard column as the impulse response technique. The standard column has been made by image processing of a finite-small-diameter-column standard sample by a software elimination technique. We demonstrated how to obtain the 3-D atomic force microscope (AFM) pyramidal tip shape using a commercial pyramidal tip and a 665-nm-diameter-column sample. The estimated tip radii are 10–15 nm in various profiles of the top. The results indicate that the method is effective to estimate a 3-D AFM tip structure in order to obtain an accurate AFM image.

We developed an atomic switch consisting of an ionic and electronic mixed conductor electrode and a counter metal electrode, having a space of about 1 nm between them. Formation and annihilation of a conductive atomic bridge is controlled using a solid electrochemical reaction, which is caused by applying a certain bias voltage between the electrodes. In this study, we measured the switching time of atomic switches made of silver sulfide and copper sulfide. The switching times were different, and this difference can be attributed to the different activation energies and chemical potentials of the materials.

We have studied a possibility to form nanometer-sized optical probe using prototype atomic force cantilevered SNOM and some fine structure samples. The system has an ability to obtain both atomic force microscope (AFM) and scanning near-field microscope (SNOM) images simultaneously. The fine optical probe was studied using the outside and inside Au coated SNOM probe. As experimental results, we have obtained a 10 nm-sized optical probe by observations of magneto-optical (MO) disc and Au thin film with many fine cracks.

A confined-chalcogenide (CC) cell structure for reducing the reset current of phase-change random access memory (PRAM) is proposed in this investigation. Both single normal-bottom-contact (NBC) (for reference) and proposed CC PRAM cells are simulated by two-dimensional finite element modelling. The simulated amorphous region of the NBC cell after reset operation is generally a semiellipse, which agrees very well with the reported experimental results. The CC cell has a rectangular amorphous region after reset operation. The reset operation current of the CC cell is much lower than that of the NBC cell. The CC cell structure needs a low reset current and a low power consumption and has a simple configuration.

We have fabricated and studied single lateral phase-change random-access-memory (PRAM), which has a confined Ge2Sb2Te5 (GST) channel connected by two wide TiN electrodes of relatively low resistivity. Its switching current for Reset operation could be as low as 4–20 µA, about one or two orders of magnitude lower than that of the conventional bottom contact PRAM cell. Its corresponding switching power for Reset operation is about 2–4 µW. The reason for such ultra low Reset current and power could be that Joule heating occurred mainly in the GST channel, instead of the resistive heater in the conventional PRAM cell.

We have developed a novel AFM (atomic force microscope) measurement technique which can examine side-walls of fine patterns etched into wafers. This technique uses a sharpen tip tilted at an angle in combination with a "step-in" mode operation, and is thus referred as "tilt-step-in" mode. This method allows one to measure side wall shape including under cut and line edge roughness (LER).

A novel memory effect in metal–chalcogenide–metal structures was observed using chalcogenide films connected by two Al electrodes. A bias polarity-dependent switching between a high (RESET) and low (SET) resistance state was observed in current–voltage characteristics of the structure when sweeping voltage in forward and backward directions. The reversible SET/RESET switching was induced by voltage pulses and their polarity. The resistances of the structure changed over a range of approximately two orders of magnitude. In readouts of the resistance, we obtained its retention time for data over 17 days at room temperature.

We studied phase-change channel transistor memory devices with an ultrathin Ge2Sb2Te5 chalcogenide film channel and tried to demonstrate two combined functions (memory: resistance change and selection: channel current control) by annealing in this paper. Drain–source resistance can be markedly decreased by 2 – 3 orders of magnitude after annealing due to the phase change from the amorphous to crystalline phases. A channel current control effect in which the drain current decreases with the gate voltage was clearly observed in 10- and 20-nm-thick Ge2Sb2Te5 devices. The absolute channel current modulation by the gate voltage in the crystalline state is much stronger than that in the amorphous state. Furthermore, the channel current control ability in devices with thin Ge2Sb2Te5 is stronger than that in devices with thick Ge2Sb2Te5. The channel current control effect might result from the potential change of the ultrathin Ge2Sb2Te5 channel by the gate voltage. [DOI: 10.1143/JJAP.45.3238]

A self-sensing mass biosensor with a femtogram mass sensitivity has been developed using a piezoresistive microcantilever. The mass change due to antigen and antibody adsorption on the cantilever in water was detected by the resonance frequency shift of the cantilever. We constructed a prototype harmonic vibration sensor using a commercial piezoresistive cantilever, Wheatstone bridge circuits, a positive feedback controller, an exciting piezoactuator and a phase-locked loop (PLL) demodulator. As experimental results, a mass sensitivity of about 190 fg/Hz, and a mass resolution of about 500 fg were obtained in water. The mass sensitivity is 100 times higher than that of a quartz crystal oscillation method. We demonstrated that the sensor can detect the reaction between an antibody of immunoglobulin (IgG) and an antigen of egg albumen (OVA). We confirmed that the binding ratio between the antibody and the antigen was about 1 : 2. The detection method is available for allergy check because the measured reaction ratio occurring on the cantilever concurs with the theoretical method.

A new atomic force microscopy (AFM) imaging method called the step-in mode for high aspect ratio structures has been proposed and developed. In the step-in mode operation, probe scanning is performed only while a probe is far from the surface of a sample. Therefore, this method can remove frictional and torsional force acting on the probe caused by probe scanning. In high aspect ratio measurement, it is demonstrated that the position error caused by torsional force is smaller than 1 nm using the probe with an aspect ratio of 5 and that the probe tip is not damaged in the step-in mode measurement. As an experimental result, using the probe with an aspect ratio of 5, the image of a shallow trench isolation (STI) structure with a top width of 315 nm and a depth of 580 nm is faithfully obtained.

The possibility of SPM-based data storage is described regarding both its recording density and readout speed for ultrahigh density data storage. We consider their gap control to achieve high-speed readout. Suitable SPM-based storages are selected and their details are studied. As a result, scanning near-field optical microscope (SNOM)- and atomic force microscope (AFM)-based storages are expected to be candidates for future storage. SNOM-based storage is for . AFM-based storage is for . Using new force modulation AFM pit recording, an ultrahigh recording density of and a readout speed of are demonstrated.

In this study, we investigated the fast switching and resistance control in a lateral GeTe-based phase-change memory (PCM). The resistivity of GeTe as a function of annealing temperature showed that it changed by more than 6 orders of magnitude in a very narrow temperature range. X-ray diffraction patterns of GeTe films indicated that GeTe had only one crystal structure, that is, face-centered cubic. It was demonstrated that the lateral device with a top conducting layer had a good performance. The operation characteristics of the GeTe-based lateral PCM device showed that it could be operated even when sub-10-ns voltage pulses were applied, making it much faster than a Ge2Sb2Te5-based device. The device resistance was successfully controlled by applying a staircase-like pulse, which enables the device to be used for fast multilevel storage.

In this study, we investigated the limitations of optical reading of very fine pits using conventional optics, immersion lens optics and near-field optics. Using very fine pits 160 nm in size using a lens with a numerical aperture (NA) of 0.95 (17 Gb/in2). In addition, an oil immersion lens optics with a NA of 1.4 read fine pits only 100 nm in size (45 Gb/in2). Advanced near-field optics is a promising tool for achieving ultrahigh-density optical reading of trillion bits/in2.

An electron-beam recorder in an XY-stage-based architecture was developed for mastering optical disks. The recorder uses the single-carrier independent pit-edge recording radial partial response (SCIPER/RPR) format. An electron beam is irradiated onto a master disk on continuously moving X and Y stages that are controlled so as to draw circular traces in sine and cosine waveforms against time, respectively. High-accuracy pit recording was realized using electron-beam deflection with feedforward correction of stage positioning error. A 25-Gbit/in2 SCIPER/RPR read-only-memory test disk with an alternating pit-array pattern was fabricated using the recorder. The pit-edge accuracy was evaluated from a scanning-electron-microscope image of the pattern. The obtained accuracy values were 1.6 nm (σ) for mark pitch, 3.5 nm (σ) for track pitch, and 3.8 nm (σ) for index position, which are good values for 3-level pit-edge modulation with 30-nm steps.

N-doping into GeTe is investigated with the aim of reducing the volume change upon crystallization, which usually induces a huge internal stress in phase-change memory devices. It is demonstrated that the thickness change upon crystallization of a N-doped GeTe (GeTeN) film is almost zero when N is doped in an appropriate amount. Cracks resulting from the stress caused by volume change disappear and the mean crystal size decreases by more than 50% upon N-doping into GeTe. It is thought that the volume-change-free behaviour is due to the formation of low-density nitride and grain refinement.

We proposed a model for calculating the resist profile in electron beam drawing. The model predicts the solubility rate on the basis of the energy deposition distribution (EDD) for the development of latent patterns in the resist. By unifying the exposure dose D (via experiments) and EDDs (via calculations), we roughly determined solubility rates for three-dimensional EDDs, and established the proposed model. The development simulation was achieved by the sequential calculation method for solubility rates based on EDD which was calculated by Monte Carlo simulation. By determining a suitable EDD region to achieve good patterning, we obtained a sharp nanodot pattern of the resist. This simulation results are in good agreement with the experimental results obtained using a combination of 2.3 wt % tetramethylammonium hydroxide (TMAH) and 4 wt % NaCl as the developer. The model was demonstrated to be useful for predicting resist profiles with different experimental solubility rates of developers.

An XY-stage driving electron beam (EB) mastering system, having an improved EB deflector, was applied to high-density disk mastering with the 40-Gbit/in2 single-carrier independent pit-edge recording/radial-direction partial response (SCIPER/RPR) format. We evaluated the format for pit-edge positioning using an optical filtering technique. A pit-edge positioning accuracy of around 2-nm was obtained and this performed fairly well with the multilevel SCIPER/RPR format. A combination of 40-nm-width pits and nanometer-accuracy positioning has potential in achieving further high-density mastering.

In this study, we proposed a ring-shaped confined chalogenide (RCC) phase change memory (PCM) cell to reduce the reset current compared with a conventional normal bottom contact (NBC) cell and a conventional normal confined chalogenide (CC) cell. The finite element analysis of the proposed RCC cell was systematically conducted depending on the radius of the center SiO2 cylinder, surrounded by the phase change material. The highest temperature at different programming currents markedly increases by increasing the radius of the SiO2 cylinder. On the basis of the simulated relationships between the cell resistance and the programming current, it was demonstrated that the derived reset current of the RCC cell can be reduced to 41% of that of the conventional NBC PCM cell.

In this work, we studied the self-assembly development of a polystyrene–poly(dimethylsiloxane) (PS–PDMS) block copolymer with molecular weight of 7,000–1,500, which has potential to form nanodots with size of several nanometers. Annealing time and temperature were intensively investigated. Distinct nanodots with a size of 6 nm and a pitch of 13 nm were obtained at a low annealing temperature of 130 °C, and nanodots with a size of 5 nm and a pitch of 12 nm were obtained at an annealing temperature of 170 °C. It was found that nanodots were formed when annealing time was reduced to as short as 6 h. This technique implies the possible high-throughput and low-cost fabrication of magnetic recording media with a density of up to 5.17 Tbit/in.2.

We report current-driven crystallization in a TiSi3/Ge2Sb2Te5/TiN vertical cell, which can be well controlled and is expected to be applied to multilevel storage with a low threshold voltage of about 1 V. We demonstrate that the number of distinct resistance levels can readily reach 8 and even higher. These levels in this study result from the initial threshold switching and the subsequent current-controlled crystallization induced by Joule heating. The latter allows the creation of many distinct levels, thus enabling the low-cost ultrahigh-density nonvolatile memory.

We investigate the effect of the staircase-shaped pulse with two subpulses on programming characteristics in the double-layered phase-change memory for freely achievable multilevel storage. Phase-change material is melted during the first subpulse and the second one is used for controlling the total crystallinity after melting because it generally acts as crystallization time. Our finite-element analysis shows that the shorter the second subpulse is, the lower the crystallinity is. It is experimentally demonstrated that the device resistance increases with decreasing the width of the second subpulse owing to the decreasing crystallinity. This implies that any resistance levels are expected to be freely achieved by staircase-shaped pulse programming.

In this study, we investigated the control of the orientation and ordering of self-assembled nanodots from a block copolymer (BCP) with the help of a guide pattern created by electron beam (EB) drawing. The guide pattern consisted of a post lattice and guide lines. The former is used to enable self-assembled nanodots from the BCP to be regularly arranged, while the latter is used to control the orientation of the nanodot arrays. It was demonstrated that the combined guide pattern was effective for controlling the BCP dot array to achieve long-range ordering and controlled orientation.

We studied the possibility of forming ultrahigh-density fine dot arrays using 30-keV electron beam (EB) drawing for 2 Tbit/in.2 patterned media. We investigated the effects of calixarene resist thickness and exposure dosage on the drawing of dot arrays with a minimum pitch. We found that the 13-nm-thick calixarene resist was very suitable for forming resist dot arrays with a pitch of 20 nm. Furthermore, the allowable region of proper exposure dosage became narrow as the pitch decreased. It is clarified that there exists a minimum pitch of 18 nm in drawing ultrahigh density fine dot arrays with a 13-nm-thick resist.

In this study, we present the physical images of multilevel storage (MLS) in both vertical and lateral phase change memory (PCM) devices and investigate MLS in a lateral PCM device with an additional top heater (LTH-PCM). The active layers above two lateral electrodes consist of a 50-nm-thick TiN layer as a top heater and a 150-nm-thick N-doped Sb2Te3 layer. A number of distinct intermediate levels are obtained by current sweeping or pulse application. According to our analysis, MLS in our devices results mainly from the gradual crystallization between electrodes by Joule heating.

In this study, we investigate the properties of Ti-Si-N films for the application as the heating layers in phase-change memory (PCM). The experimental results show that the resistivity of Ti-Si-N films can be varied by over six orders of magnitude from 4 10 18 . 2 − × to 2 10 9 . 3 × cm ⋅ Ω by increasing the flow rate ratio (N2/(N2+Ar)) from 0 to 10%. The controllability of resistivity might result from the concentration change from Ti-Si to mixture of TiN and Si3N4. Reversible switching was also successfully demonstrated by using a lateral PCM with these heating layers. The stability of the Ti-Si-N films at high temperatures implies that they can be used as the heating layers in the conventional vertical PCMs for current reduction.

We studied proximity effect in 30 keV electron beam (EB) drawing with calixarene resist for patterned media and quantum devices. Using about 15-nm-thick calixarene resist on Si substrate in conventional EB drawing system, the proximity effect has been studied by forming and observing 20-, 25-, 30-, and 40-nm-pitch resist dot arrays and measuring exposure dosage intensity distribution (EID) function. As a result, the proximity effect is negligible small due to comparing with some dot sizes in center, side and corner of 2 µm square with 25×25 nm2 pitch dot arrays. In addition, the proximity effect parameter η in EID function is less than 0.3. It is clear that the EB drawing and calixarene resist system is very suitable for forming ultrahigh packed dot arrays pattern. We demonstrated 20×20 nm2 pitch resist dot arrays (about 1.6 Tb/in.2) with a dot diameter of about 14 nm and the same size as everywhere in the pattern.

We have developed a high-precision atomic force microscope (AFM) for measuring fine pattern structures for semiconductor process evaluation. Three-axis ultrahigh-resolution displacement sensors using modularized laser interferometers were built into an AFM scanner combined with piezoactuators, elastic parallel-plate structures and an on-axis optical microscope. A newly designed symmetrical layout of the optical path of homodyne interferometers and a digital signal processor (DSP) enabled highly stable measurements of the mechanical displacements of the tip of an AFM scanner. As a result of their ultrafine positioning capabilities, a resolution of the displacement sensors of 0.05 nm was achieved. The periodic error of laser waves was compensated by employing DSP-based processing. Thus, a wide linearity range from 0.1 to 1000 nm was demonstrated and a one-sigma repeatability of 0.25 nm was obtained by measuring reference samples of 50 and 1000 nm step heights. Finally, micro-roughness with a 0.1 nm height, a GaAs atomic step with a 0.3 nm height, patterns with high aspect ratios, and resist patterns were clearly observed using an interferometer displacement signal.

The programming characteristics of a phase-change memory (PCM) cell with a chalcogenide layer contacted by a resistive heater are investigated by finite element modelling. As analyzed in this study, the characteristics are markedly affected by the resistivity of the phase-change chalcogenide material. A higher reset current of 1.6 mA is required for the as-fabricated virgin PCM than that of 1.3 mA for the cycled PCM because of the resistivity difference of the chalcogenides in the two cases. More importantly, a chalcogenide layer with a much higher resistivity than the resistive heater is necessarily adopted for a higher energy efficiency to markedly reduce reset current to 0.6 mA or even lower while slightly increasing reset voltage.

We have developed a new critical dimension (CD) measurement technique using atomic force microscope (AFM) which can measure width-dimensions and examine sidewall-shapes of fine patterns on a wafer. The technique employs a flared-type tip in combination with digital probing and multi-angle scanning mechanism that allows the tip to trace the sidewalls on both sides of a feature (or trench) by making physical contacts with the sidewall surface. First, by using finite element method (FEM) we analyzed deformation of the tip and cantilever to compensate errors caused by the deformation. To verify our compensation method we measured quartz reference patterns either with perpendicular sidewalls or undercuts. In this paper we will describe the applications and usefulness of this multi-angle operation and show some measurement results of ArF resist patterns with 200 nm width and 400 nm depth that were obtained with a flared tip of 120 nm diameter.

We studied the electrical properties of 20- and 50-nm-thick Ge2Sb2Te5 and AgInSbTe films for nonvolatile lateral transistor memory devices. Both kinds of thin films were prepared as film samples and device samples which were then annealed at temperatures from 140 to 415°C. It is known that crystal size can be effectively reduced with film thickness on the basis of X-ray diffraction analysis. The resistances of all film samples annealed at 140–415°C decreased by approximately 5–6 orders of magnitude. In the case of device samples, however, the source-drain resistances of Ge2Sb2Te5 samples were first reduced and then reversely increased and it seemed that the resistances of AgInSbTe samples did not drop. The abnormal resistance increase above the crystallization temperature may be caused by phase change and thermal expansion, as we analyzed in this paper. Finally, the resistance changes of device samples with channel lengths in the range of 0.4–3 µm were discussed from the point of view of miniaturizing the phase change memory device.

Atomic force cantilevered scanning near-field optical microscopy (ANOM) has been proposed for observing a micromagnetic structure of a recorded magneto-optical (MO) disc. The prototype system has an ability to obtain both atomic force microscopy (AFM) and scanning near-field microscopy (SNOM) images simultaneously. This system has some special functions: (1) it keeps the sample-probe gap constant with atomic force and an AFM cantilever, (2) it generates near-field light from the small aperture formed on the tip of the cantilever, (3) it uses a polarized light in the laser beam illumination and detection systems, and (4) it adjusts laser beams incident on fixed positions of the cantilever in ANOM optics. As an experimental result, we obtained SNOM and contact mode AFM images of a commercial MO disc. We can detect a polarized plane at a minimum angle of less than 0.2 deg. and observe submicron recorded magnetic domains on a 640 MB MO disc.

A harmonic vibrator using a piezoresistive cantilever has been developed for a picogram mass biosensor. We constructed a prototype vibrator sensor using the cantilever, Wheatstone bridge circuits, positive feedback controller, a piezoactuator and a phase-locked loop (PLL) demodulator. As experimental results, a mass sensitivity of 2.2 pg/Hz was obtained from water molecular adsorption on the cantilever. We confirmed that the mechanism of water molecular growth has 2 modes, island growth and layer growth. The critical point of the mechanism change was a humidity of about 42%. At the critical point, the adsorbed mass corresponds to the water layer of about 13 monolayers.

A new atomic force microscope (AFM) imaging has been used to study the bending of a sharpened and slim probe in the digital probing method (step-in mode) for the critical dimension (CD)-AFM technique. The bending of the AFM probe indicates a serious problem in measuring very fine patterns with a high aspect ratio with an error of less than 1 nm when we use the sharpened and slim probe. In our estimation, position errors Δr (in plane) and Δz (in perpendicular) rapidly increase with the slope angle and a controlled force. In experiments, we measured a degradation of the pattern profile as the controlled force increased in the AFM system. We have to control the probe at a force of 5 accurately.

A microsensor with a picogram mass sensitivity has been researched using the resonance frequency shift of an atomic force microscope (AFM) cantilever. The mass change of the water molecules adsorbed on the cantilever was measured by analyzing the resonance frequency shift using a laser beam deflection detection system. As experimental results, a sensitivity of about 2 pg/Hz was obtained. The mass change due to increasing humidity showed that the mechanism of water molecular growth changed from an island growth to a layer growth. The critical point of the mechanism change was a humidity of about 60%. The adsorbed mass corresponds to a water layer of about 12 monolayers.

Cantilevers as small as 10 µm in length are required in order to achieve a practical data transfer rate in a read-only memory system using cantilevers as head. Thus, a new optical lever design concept that can detect the motion of such small cantilevers is necessary. The new optical lever concept that we propose makes it possible to use an objective lens with a high numerical aperture and to reduce the expansion rate of the projected light source image on the cantilever surface. As a result, we were able to reduce the incident laser spot diameter to 5 µm. It was also possible to expand the operation bandwidth to 10 MHz while achieving a displacement sensitivity of 0.48 Å (when a 10-µm long cantilever was used) by using a small spot position sensor, because the laser spot diameter on the detector could to be reduced to an arbitrary size.

A cavity-SNOM (scanning near-field optical microscope) head using a laser diode is proposed and studied theoretically and experimentally. Theoretically, we study the optical properties using conventional rate equations. Several conditions to detect the SNOM signal with a photodiode are discussed. Experimentally, the dependence of output power of the laser diode on the injection current is measured. A sufficiently strong modulation signal is detected using a tapered fiber as the probe, but no modulation signal is detected using a tapered fiber with a small aperture (SNOM probe). The conditions for detecting a signal using a SNOM probe are also discussed, and we suggest that a laser diode with a SNOM probe fabricated on its facet is essential for realizing a practical cavity-SNOM head.

In this paper we describe a narrow pitch tracking method for data storage using an atomic force microscope (AFM) probe head. A track position of the AFM head on a recording disk was controlled by an optical tracking method. Narrowing of the track pitch was achieved by locating eight recording tracks in one groove of the disk. These track positions were controlled by eight phase tracking-error signals which were created from one groove of the disk. In writing, we used the force modulation recording method which forms written pits by applying force pulses between the AFM tip and the polycarbonate recording disk. Using the recording system, we achieved 200 nm pitch tracking control and readout from written pits as small as 40 nm in diameter. A scanning electron micrograph of the written pits showed that the tracking accuracy was about 20 nm.

We performed thermal simulation of nanostructure modifications through point heating of phase-change materials using a scanning near-field optical microscope (SNOM). As the recording process, two major heating mechanisms were considered: direct heating by near-field light and thermal conduction from the SNOM tip heated by the incident light. The temperature increases in the sample due to these heating mechanisms were calculated for GeSbTe phase-change thin films. It was found that thermal conduction from the tip was the dominant process for heating and its temperature increase was more than three times larger than that of direct heating by near-field light.

We present for the first time a nanometer-sized phase-change recording using a scanning near-field optical microscope (PC-SNOM recording). The recording experiments were performed with a SNOM using a 785-nm-wavelength semiconductor laser diode, shear force detection for gap control and reflected light detection for observing the domains (reading). The recording media of ZnS·SiO2(20 nm)/GeSbTe(30 nm)/ZnS·SiO2(150 nm)/polycarbonate substrate were used. The writings were done at laser powers of 8.4–7.3 mW in the probe for pulse widths of 5 or 0.5 ms. As a result, we obtained a minimum recorded domain size of 60 nm in diameter. This size shows a potential to achieve an ultrahigh density PC-SNOM recording with about 170 Gb/in2. A possibility of achieving high speed readout for the future data storage is also discussed.

A noncontact scanning force microscope employing a novel tip height control system using phase lock technology has been developed. An oscillator using a cantilever as a mechanical resonator is used as a voltage controlled oscillator in a phase locked loop, and its output signal is phase locked to a high-precision signal source. Its most remarkable feature is that this tip height control is unconditionally stable. Thus, it was possible to realize the desired system response by adjusting the loop parameters. Its efficiency was demonstrated by imaging the surface of a magneto-optical disk at the lowest tip height which was impossible to achieve with a conventional servo technology.

The high spatial resolution of a magnetic force microscope (MFM) has been studied with respect to a tip-sample separation, theoretically and experimentally. In the estimations, the MFM resolution becomes high as the separation decreases. The separation of less than 1 nm provides an advanced resolution of less than 10 nm. In the experiments, the probe of the conventional MFM cannot be allowed to come within 10∼20 nm of the sample to avoid mixing the atomic force with the magnetic force. By contrast, just-on-surface-MFM (JS-MFM), which allows for the MFM measurement at a small separation within 1 nm, can provide a detailed observation of the localized surface magnetic stray field with an advanced resolution of less than 10 nm.

Nanometer recording has been demonstrated with tens nanometer diameter pits and gold mounds formed on graphite and Si substrate using an atomic force microscope at atmospheric pressure. The probe is prepared by means of coating thin gold film on an SiO2 birdbeak-type cantilever probe, fabricated by a Si microprocess. Applications of voltage pulses between the probe and the graphite make about 10-nm diameter pits and Au mounds. Furthermore, about 50-nm to 30-nm diameter Au mound formations on Si wafer covered with natural silicon oxide are also demonstrated. The results indicate that the technique has potentials to achieve Tera-bit/in2 highly packed storage in air, and directly to write nanometer sized patterns on an insulating thin film.

Gold adsorption onto a Si(111)7×7 surface is studied in situ by Scanning Tunneling Microscopy (STM). Gold is deposited onto the Si(111)7×7 surface, kept at 500°C during the STM observation. The 5×2 structure grows at a step edge and expands towards both the higher and lower terraces. Si islands are also formed during the gold deposition. These phenomena are explained by the production and migration of excess Si atoms during the phase transition from the 7×7 to the 5×2 structure.

A magnetic force microscope (MFM) is developed, which is capable of operation in both DC and AC detection modes, to allow observation of topographic and magnetic structures in the same sample area. An optical lever sensor is introduced to measure the cantilever displacement. DC detection senses the repulsive atomic force between the tip and a sample to provide surface topography information. AC detection senses the force gradient acting on an oscillating tip in the stray magnetic field emanating from the sample to provide magnetic information. A fabrication method for a sharp magnetic tips is also described. A comparison of the magnetization and surface structure images of a thin film medium observed by the MFM shows that nanometer-level roughness on the medium surface can affect the magnetic recording process.

A 3-dimensional (3-D) magnetic stray field and the surface structure have been observed using an atomic and magnetic force microscope (A/MFM) with an optical-beam-deflection force detector. Measurement is carried out by operating the microscope as a surface structure observer in constant repulsive force AFM mode. The 3-D magnetic stray field measurement is done in force gradient MFM mode with probe position control above the surface. Initial results have demonstrated that the 3-D magnetic stray field and surface structure of magneto-optical disk can be imaged simultaneously.

Polycrystalline silicon films were deposited on SiO2, and arsenic ions were implanted into these films. The Hall and resistivity measurements show that the mobility lowering effect and the activity lowering effect dominate the electrical properties of the films. Tunneling barrier height images also suggest carrier trapping at grain boundaries in lightly doped cases, indicating the possibility of arsenic segregation. These results indicate that the mechanism of the mobility lowering effect is mainly governed by the carrier trapping at grain boundaries.

An estimation of the radiation damage and pattern resolution in ion direct writing is presented by a Monte Carlo simulation of the slowing down and scattering of low-energy ions and recoiled atoms in an amorphous target. The simulation program is characterized by employing the power of a logarithm approximation as a screening function, the distance between collisions and a modified step length based on a binary collision model. Calculated results are in terms of radiation damage depth and fine pattern resolution using sputtering and radiation damage as a semiconductor fabrication technique. Consequently, available informations can be obtained as ion lithography using sputtering and radiation damage that has a much finer pattern resolution (less than a few 10s Å) than electron beam lithography using a latent resust image.