Reflection-mode Scanning Near-field Optical Microscope Research Articles

Hybrid STM/R-SNOM with novel probe

A reflection-mode scanning near-field optical microscope joined with scanning tunneling microscope having a common revolving detection head and mounted on a classical optical microscope stage is proposed. This arrangement combines advantages of both near-field and far-field imageries and is able to display the images of surfaces with superresolution beyond the diffraction limit. Its function is characterized by the wide range of resolution and/or by the possibility to study different kinds of surfaces with nanometer-scale accuracy. A novel probe is used in the optical stage of the microscope. During its fabrication the light power of an Ar–Kr laser coupled to the single-mode fiber allows a local heating of a buffered HF solution in the vicinity of the extremity of fiber. By tuning the output power of the laser, the flux of energy at the very tip of the fiber varies, and different cone angles of the probe could be obtained. This process is faster than the classical chemical etching. The etching speed, and shapes of the fiber versus temperature are therefore discussed. A comparison of the two different images obtained with a STM and R-SNOM parts of the microscope is also presented.

Kerr-effect based magneto-optic imaging with sub-100 nm resolution (abstract)

Magneto-optic imaging based on Faraday rotation with lateral resolution of about 60 nm was successfully demonstrated recently using scanning near-field optical microscopy.1 Magnetic contrast based on the Kerr effect with similar resolution still remains a challenge. Due to numerous applications of the Kerr effect this problem is of significant technical and scientific interest. Demonstration of such a contrast based on Kerr effect obtained using near-field optics is the subject of the present work. We have developed a reflection-mode scanning near-field optical microscope (SNOM) that is routinely capable of imaging with 30–50 nm resolution. It is based on a metal coated fiber probe with the light of a diode laser (λ=635 nm) coupled into it. Distance between the scanning probe and the sample is maintained constant at 5–10 nm using a shear force based feedback. Light reflected from the sample is collected with an elliptic mirror and a photomultiplier. We have studied the dependence of polarization of light reflected from the various nonmagnetic metal and dielectric surfaces upon the distance between the probe and the surface. Mechanisms responsible for the change in polarization of the reflected light are analyzed. Finally a periodic array of domains was written in a Co/Pt multilayer film using optical thermomagnetic recording. The domains were imaged using a magnetic force microscopy technique that indicated that the size of the domain was about 400 nm. The domains were then imaged using our reflection-mode SNOM. Features of domains smaller than 100 nm in size are clearly resolved. Values of conventional polar Kerr rotation are compared with ones detected using the SNOM.

Observation of magnetic domains using a reflection-mode scanning near-field optical microscope

It is demonstrated that it is possible to image magnetic domains with a resolution of better than 60 nm with the Kerr effect in a reflection-mode scanning near-field optical microscope. Images taken of tracks of thermomagnetically prewritten bits in a Co/Pt multilayer structure magnetized out-of plane showed optical features in a track pattern whose appearance was determined by the position of an analyzer in front of the photomultiplier tube. These features were not apparent in the topography, showing this to be a purely magneto-optic effect.