Weak electron emission current for characterization of nanomaterials, gas and radiation sensing towards medical applications

Abstract

Rapid development of nanomaterials opens a wide horizon for their applications, medicine being one of them. Nanomaterials and nanodevices are in use both in the human body and as medical nanosensors. Reliable employment of materials requires trustworthy detection of their properties. Characterization of both the nanomaterials and nanosensors should be supplied at the nanoscaled dimension. To avoid disturbing gentle nanoobjects, measurements of them with contactless techniques are preferable. Low energy electron has a mean free path in a solid that is of the order of nanoscale. Therefore, a prethreshold (energy of the emitting electron is close to the electron work function) electron emission contactless spectroscopy could become an efficient instrument both for characterization of nanostructured materials and nanosensing. Weak emission (~ 10 -16 …10 -15 Q/cm 2 ) of electrons from a solid does not give a significant feedback to measurements in the sense of the negligible inducted electrical charge at the material surface (the density of the surface electrons in the solid is around 10 14 cm -2 ). The paper reviews photo-, dual-, and exo-electron emission fundamentals and their applications for the characterization of nanoobjects (concentration of pointlike 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. The ways for medical applications are indicated.

Thermal Oxidation of Tungsten Coatings for Detection by Infrared Spectrometry Method

“…Characterization of the crystal structure of W is important to improve the knowledge about stability properties of layers, the quality depending on production process and their composition. Sensitivity against changes in surface structure is essential in the development of stable operating devices using W. On nanometer scale precipitated W on dielectric silicon (Si) -silicon dioxide (SiO2) layer bases enable high thermal resistance and other conditions for fabricating semiconductor integrated audio amplifiers and microtriodes [7]. In the process of production, it is essential to check the homogeneity and quality of the synthesized films for further production of microtriodes from W thin films on Si-SiO2 substrate.…”