Sample Paper on Nuclear Microscopy

A nuclear microscopy is a tool used to study surfaces and interfaces. The tool studies ion-solid interaction on surfaces. The interaction explains the process behind ion scattering. In the study, the projectile used transfers energy to the target nucleus. This energy causes neutron to be ionized which makes the target ions to be elementary excited. When two elastic bodies collide in the presence of this energy, it leads to kinematic factor. This is due to collision of nucleus and target atoms. The collision leads to scattering cross section. As the projectile passes through a denser solid medium, it losses energy hence stops the factor. This statistical fluctuation causes energy staggering resulting to loss of mass and depth resolution. At lower energies, nucleus continually losses energy while at higher energy, the electrons losses energy as well, which leads stoppage of ion collision.

The reduction of depth resolution due to energy staggering is useful in ion channeling. Ion channeling is applied in crystallization process and recrystallization as well. It can also be used in the locating lattice of foreign atoms whether implanted or diffused and finally, it is applied in the analysis of oriented film growth. The parameters for ion channeling include transverse energy, critical angle, continued model, minimum yield, energy loss, flux distributions, and dechanneling.Channeling target chamber and the channeling scan are instruments used to observe channeling spectra. Analysis of nuclear reactions differs with the metals used. The analysis is better for light elements like B, C, N and O.On the other hand, RBS is good for heavier metals on light substrates.

Nuclear microscopy reduces the size of a beam from MM to the micro millimeter to nm. This is because it uses a series of magnetic lenses for focusing, ranging from doublet to triplet to quadruplet of a quadruple lens system. The beam is scanned by magnetic deflectors which are also operational in a vacuum. The tool is, therefore, functional for micro analysis. In ion interactions, the ion path has three features. First, the degree of scattering per collision is small because of the ions travels in an approximately straight line. Therefore, they do not suffer large angle collision. Secondly, ion travels through many atomic layers on the surface before they come to rest and therefore the range is relatively high and increases with how energetic the ions are. For example, protons range is higher than electrons because they are more energetic. The third feature of ion path is that the relatively high range enables extraction of more energy for example, below the surface of the sample in case of protons. The degree of staggering is usually small because the statistical nature of the collision process is small. Ions, therefore, stop at approximately the same depth in a sample.

            Some applications of micro beam arrangements include elemental imaging, channeling contrast microscopy and proton beam writing. Apart from analyzing atoms on solid surfaces, nuclear microscopy is used to analyze gas -solid interfaces. A variety of spectroscopies can be used to analyze a surface of metal before and after a gas/impurity atom adsorption. Most of the surface spectroscopies give evidence of this adsorption. An example is Carbide formation on Ni (100) as results of CO adsorption on Ni.However, there are problems associated with this analysis including high pressure, high temperature, lack of depth information and lack of lattice location. A situ lattice location can be developed under these conditions by choosing a single crystal substrate in situ deposition and measuring the concentration and location of atoms adsorbed at these conditions to form thin windows. Nuclear microscopy is therefore both a qualitative and quantitative tool that can be manipulated to analyze both ion and gas surfaces.