Atomic liquid imaging

Much is known about the growth, crystallography and reconstruction of semiconductor (SC) surfaces from STM ultrahigh vacuum experiments. In this environment the first atomic resolution image was obtained for a semiconductor subslralc" before it was done for metal substrate. In the case of air and in particular in liquid enviromnent the situation is different. This is because of the presence of the native oxides formed in air on SC surface, and corrosion processes taking place easily in solution. 

Atomic force microscopy (AFM) enables the visualisation of biopolymers in their native hydrated state [ 1,2] in liquid, in a partially dehydrated state in air, in a dehydrated state in an ultra-high vacuum, or in their frozen state with cryogenic AFM. Liquid imaging is often preferred where there is a desire to observe dynamic events, or acquire more biologically relevant data [1,3-6]. The data obtained from AFM may also be more biologically relevant, as no... 

To clarify these points, the author and coworkers carried out detailed experiments to compare the noise measured with the actual instruments and the noise expected from the operation principle. The results revealed that FM-AFM performance in air and liquid was limited not only by the Q factor but also by the noise from the cantilever deflection sensor. By developing a low-noise cantilever deflection sensor, true atomic-resolution imaging by FM-AFM became possible even in liquid in 2005. This dramatic improvement of FM-AFM performance in liquid triggered subsequent applications of FM-AFM to the studies in biology and chemistry. 

This result was soon confirmed by another research group. Hoogenboom et ah developed a low-noise cantilever deflection sensor using a Fabiy-Perot interferometer. With this deflection sensor, they obtained molecular-scale images of bR trimers and atomic-scale images of mica by FM-AFM in liquid. ... 

Until recently, the use of FM-AFM in liquid was very limited. However, several AFM research groups have already started to use it for their own applications. Kawakatsu et al developed a low-noise cantilever deflection sensor using a Doppler interferometer and obtained atomic-resolution images of mica in liquid. Umeda et al. reduced the deflection noise by modifying the cantilever... 

Hansma H G, Vesenka J, Siegerist C, Kelderman G, Morrett H, Sinsheimer R L, Bustamante C, Elings V and Hansma P K 1992 Reproducible imaging and dissection of plasmid DNA under liquid with the atomic force microscope Science 256 1180... 

The atom probe field-ion microscope (APFIM) and its subsequent developments, the position-sensitive atom probe (POSAP) and the pulsed laser atom probe (PLAP), have the ultimate sensitivity in compositional analysis (i.e. single atoms). FIM is purely an imaging technique in which the specimen in the form of a needle with a very fine point (radius 10-100 nm) is at low temperature (liquid nitrogen or helium) and surrounded by a noble gas (He, Ne, or Ar) at 10 -10 Pa. A fluorescent screen or a... 

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