This paper discusses the principles of magnetic force microscopy (MFM) and its application to magnetic recording studies. We use the ac detection method which senses the force gradient acting on a small magnetic tip due to fields emanating from the domain structure in the sample. Tip fabrication procedures are described for two types of magnetic tips: etched tungsten wires with a sputter‐deposited magnetic coating and etched nickel wires. The etched nickel wires are shown to have an apex radius on the order of 30 nm and a taper half‐angle of approximately 3°. Lorentz‐mode transmission electron microscopy of the nickel tips reveals that the final 20 μm is essentially single domain with magnetization approximately parallel with the tip axis. Images of written bit transitions are presented for several types of magnetic media, including CoPtCr, CoSm, and CoCr thin films, as well as γ‐Fe2O3 particulate media. In general, the written magnetization patterns are seen with high contrast and with resolution better ...

Magnetic force microscopy: General principles and application to longitudinal recording media

With the rapid development of technologies for the fabrication of, as well as applications of low-dimensional structures, the demands on characterization techniques increase. Spatial resolution is especially crucial, where techniques for probing the properties of very small volumes, in the extreme case quantum structures, are essential. In this article we review the state-of-the-art in local probe techniques for studying the properties of nanostructures, concentrating on methods involving monitoring the properties related to photon emission. These techniques are sensitive enough to reveal the electronic structure of low-dimensional semiconductor structures and are, therefore, able to give detailed information about the geometrical structure, including fabrication-related inhomogeneities within an ensemble of structures. The local luminescence probe techniques discussed in this review article can be divided into four categories according to the excitation source: (i) spatially localized microphotoluminescence spectroscopy using either strong focusing or masking; (ii) near-field optical microscopy to reach below the diffraction limitation of far-field optics, by either exciting, detecting, or both exciting and detecting in the near field; (iii) cathodoluminescence using focused energetic electrons in an electron microscope; and (iv) scanning tunneling luminescence, using low-energy electrons injected or extracted from the tip of a scanning tunneling microscope.

Local probe techniques for luminescence studies of low-dimensional semiconductor structures

There is provided a scanning probe microscopy comprising a probe 6 situated to face the surface of an sample 1, a first piezoelectric element 8 for moving the sample 1 and the probe 6 relative to each other in a first direction perpendicular to the surface of the sample, and second and third piezoelectric elements 3 and 4 for moving the probe and the sample relative to each other in second and third directions perpendicular to the first direction, thereby enabling the probe to scan the surface of the sample, wherein at least one of the first to third piezoelectric elements 8, 3 and 4, which is closest to the sample 1, is formed of a single crystal.

Scanning Probe Microscopy

An apparatus and method for scanning a probe over a surface to either produce a measurement of the surface representative of a parameter other than the topography of the surface or to perform a task on the surface. The scanning operation is divided into two parts and with a first scan to obtain and store topographical information and with a second scan to measure the parameter of the surface other than topography or to perform the task while the probe height is controlled using the stored topographic information.

Scanning probe microscope using stored data for vertical probe positioning

The analysis of photons emitted from the tip–surface region of an STM has produced new information on local dissipative processes in tunneling. A key objective to extend our work to a general spectroscopic and microscopic method is to collect and detect photons as efficiently as possible and here we describe our experimental arrangements, one of which incorporates an ellipsoidal mirror and the other a lens system to collect the photons. The systems operate in UHV and have in situ sample and tip transfer facilities. Examples of a variety of photon spectroscopy modes including photon spectra, isochromat spectra, angular distributions, and photon mapping are presented.

Photon emission scanning tunneling microscope

Using electroluminescence associated with scanning tunneling microscope in AlxGa1−xAs heterostructures, we show that: (a) luminescence due to recombination can be induced within single quantum wells of dimensions down to a few nm and can also be used to image them, (b) the energy of bulk bands can be determined, and (c) transport parameters can be measured, e.g., the thermalization length and the diffusion length of minority electrons. This technique opens up new possibilities for the study and characterization of semiconductors and devices—including the possibility of studying surface states and single trapping centers associated with lattice defects, impurities, chemisorbed species, etc.

Luminescence in scanning tunneling microscopy on III–V nanostructures

Several techniques are presented which allow magnetic force microscopy to be performed while simultaneously mapping the surface topographic features of a magnetic sample. The separation of magnetic and topographic features measured simultaneously with a scanning force microscope is made possible by an instrument based on a differential interferometer that can detect cantilever deflections of 0.005 nm at a frequency as low as 1 Hz. Two different applications are presented.

Separation of magnetic and topographic effects in force microscopy

A three‐dimensional image of the surface roughness of four conducting iron‐oxide Fe3O4 thin films was obtained using a scanning tunneling microscope. We obtain grain size and surface roughness of films deposited on Si(100) by reactive sputtering at different substrate temperatures. The apparent grain size lies between 10 and 50 nm, and depends on the substrate temperature and film thickness. We have also determined the scanning tunneling microscopy parameters (tip size and shape) to obtain ‘‘real’’ images (i.e., images without artifacts) of the films.

Scanning tunneling microscopy as a tool to study surface roughness of sputtered thin films

The scanning force microscopy is used to charge insulating films locally and to monitor the decay thereafter. On Si3N4 films the charge decay shows up as a discontinuous staircase, demonstrating single charge carrier resolution. The decay is controlled by thermionic emission. The smallest charge amount transferred into a PMMA film was only one or two electrons. The imaged charge area showed no broadening with time, indicating that the excess carriers are immobile.

Probing single charges by scanning force microscopy

The tip of a scanning tunneling microscope is used as a source of ultralow-energy electrons to excite luminescence in model AlGaAs/GaAs(001) heterostructures. This beam injection technique has the advantage of providing a nanometer-sized charge generation volume. We demonstrate the application of this technique to determine minority charge carrier transport parameters such as the thermalization length of hot electrons and the diffusion length of minority electrons.

/pdf/high-resolution-electron-beam-injection-in-semiconductors-qn6wbigwg8.pdf

High-resolution electron-beam injection in semiconductors using a scanning tunneling microscope

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