Prethreshold electron emission towards medical applications: characterization of nanomaterials, gas and radiation sensing (review of recent results)

Abstract

Rapid development of nanomaterials opens a wide horizon for their medical applications in nanovolumes both of the human body and sensors. Safe employment of materials in a human organism requires reliable detection of their properties. Characterization of both nano materials and nano sensors should be supplied at the nanoscaled dimension. To do not disturb gentle nanoobjects their measurements due to contact less technique are preferable. Low energy electron has a mean free path in a solid that is in order of nanoscale. Therefore, a prethreshold (energy of the emitting electron is close to the electron work function) electron emission contact less spectroscopies could become a good instrument both for characterization of nanostructured materials and nanosensing. Weak emission (~10^-15… 10^-13 Q/cm² ) of electrons from a solid does not give a significant feed back to measurements in sense of the negligible inducted electrical charge at the material surface (a density of the surface electrons in the solid is around 10¹⁴ cm^-2 ).  The paper reviews photo-, dual- and exo- electron emission fundamentals and their applications for characterization of focused to medicine nanoobjects (concentration of point like imperfections, their annealing, migration; surface charge of nanoparticles; energy gap; electron density of states; thickness of thin films and interfaces between them and the substrate) as well as gas and ionizing radiation nanodimensional sensing .