Scanning probe microscope (SPM) has increasingly attracted attention lately as powerful nanotechnology tools for observation of surface morphology, measurements of tip-surface interaction, manipulations of atoms and lithography in nanoscale. Micromachining is one key technology to generate a new silicon based probe for SPM. In order to measure the small force, microfabricated cantilever with a low spring constant is required. On the other hand high resonant frequency is required to reduce external noise and to obtain a high scan-rate. Scaling-law shows that small-sized cantilever has a low spring constant and a high resonant frequency. By etching a bulk silicon under control, extremely thin single-crystalline cantilever can be fabricated. When the motion of thin beam structure is sensed capacitively, narrowing a gap between thin cantilever and electrode is one of the most effective methods to raise the sensitivity. Therefore, a thin silicon beam having an opposed electrode with a narrow gap was fabricated for capacitive AFM probe. At the tip of cantilever, silicon-tip can be fabricated by depositing silicon atoms owing to field evaporation using ultra-high-vacuum scanning tunneling microscope.
We have developed new nano-scale material processing techniques by using the probe of scanning tunneling microscope (STM) and atomic force microscope (AFM) with a cathode in air, in which the metal thin film is selectively oxidized by anodization. We call this technique STM/AFM nano-oxidation process, and this novel processing technique was applied to the surface modification of titanium (Ti) and niobium (Nb) thin films. From both Auger electron spectroscopy (AES) analysis and electrical characteristics of planartype metal/insulator/metal (MIM) diodes, it was confirmed that the obtained modified structures are of the metal oxide. Also, by adjusting the oxidation parameters, we can get the metal oxide wires with 10 nm scale dimension. Furthermore, by applying this technique to the fabrication of single electron transistors (SETS), room temperature operation was achieved in Ti/Ti oxide-and Nb/Nb oxide-based SETs.
A nanometer-scale structure of metal/Langmuir-Blodgett (LB) film/metal is realized using an atomic force microscope (AFM) with an electrically conducting probe. In this configuration, increase in conductance can be induced at any point in the LB film by application of a voltage pulse. Clear spots are observed in the current image at the points where voltage pulses are applied, while no specific feature such as protrusions or holes is observed in the AFM image obtained simultaneously. These results show that the conductance of the LB film changes without pit formation in the LB film or metal cluster deposition from the tip of the probe. The transition takes place within 1 μs, and the transition can be induced at several thousand points, at least, without tip degradation. These facts demonstrate the feasibility of constructing information storage devices with high density.
Potential of scanning probe microscope (SPM)-based storage technique for ultrahigh density recording is presented. The SPM-based storage proposed here, STM (scanning tunneling microscope)-, AFM (atomic force microscope)-, MFM (magnetic force microscope)-, and SNOM (scanning near-field optical microscope)-based storages are described on areal density. The experimental results provide that contact type AFM-based storage is the most potential storage method for ultrahigh recording density and for high readout speed. It has the potential to achieve an ultrahigh density recording with a density of higher than 1Tb/in2 and a readout of faster than 1Mb/s.
In the applications of Scanning Probe Microscope technique to ultra-high density data storage, piezo scanners are mostly used to scan samples or probes. The scanning speed and scanning area are, therefore, limited due to the piezo scanner. In this article, we discribe the data storage technique by using disk rotating SPM. We use a SiNx-SiO2-Si substrate structure (NOS) disk as a medium in the charge trapping technique. For writing, we bring conductive probe contact with the surface of the medium, and apply voltage pulses between the probe and the medium while rotating the medium. We can verify a series of recording bits with Scanning Capcitance Microscopy and thus the bit size is 300 nm full width at half maximum. We can also obtain a signal of the change in capacitance between the probe and the Si substrate while rotating the medium.
We present recent results of synchrotron radiation photoelectron spectroscopy, ultra-violet photoelectron spectroscopy, low energy electron diffraction, scanning tunneling microscopy, and photoluminescence measurements for the horizontal Bridgman-grown GaAs(001) surface prepared by the deoxygenated and deionized water (DODIW) treatment. We discuss the relationship between surface stoichiometry, surface structure, and the pinning position of surface Fermi level for the DODIW-treated GaAs(001) surface, and point out that the position of surface Fermi level is strongly affected by crystal defects near the surface.
Artificially layered metallic and magnetic films have offered one of the most exciting and available fields in modem thin film magnetism. Recent discoveries of the remarkable magnetic features such as a giant magnetoresistance (GMR) effect, etc. have stimulated a great deal of the research activities. The recent advance in thin film growth techniques enabled us to synthesize high-quality metallic ultrathin layered heterostructures within monatomic layer accuracy, and consequently make possible to see quantum confinement effects obviously. Now, nano-structured magnetic systems with in-plane artificial periods are becoming to attract much attention as the next concept for the multilayered films. Here, we introduce the current topics of the magnetic nano-structures. First, a quantum size effect and an interlayer exchange coupling in multilayered structures are presented, and we consider the effects of lateral nano-scaling and lower demensionality. Next, we introduce fabrication methods of the nano-structures. Finally, we review our results on the magnetic properties of nanoscaled two dimensional Co dots array formed on the reconstructed Au (111) surface.
In the last decade, a number of electrostatic force microscopes (EFMs), which are based on the conventional non-contact scanning force microscope (SFM), have been developed to observe isolated surface-charges, dielectric constants of insulating films and surface potentials at the nanometer scale. Here, we describe the methods we have employed to obtain high-resolution electrical information using an EFM.