Nanotechnologies to fabricate particles, films and process surface layers are requesting for material characterization non destructive methods to get information scaled to several nanometers. Such the demands could be satisfied owing to measurements of emission of electrons when they have a nanometric mean free path within the tested object. For this the electrons have to have an energy ≤ 1 eV. Ultraviolet radiation is suitable to excite such the electrons. When temperature (T) of the tested object is a constant, ultraviolet radiation promotes classical photoelectron emission (PE), typically energy of the photons (hν) being selected close to an electron work function (ϕ), hν > ϕ. The value of ϕ, as well origin of electron transitions could be recognized because of the electron emission current (I) regularity in dependence on hν. In a case when T = var, modulation of density of electron states (N) and/or surface potential could be provided, the emission current being affected. By this way the photothermostimulated exoelectron emission (PTSE) mode is achievable. Typically N is affected owing to relaxation of point type imperfections. In such the case a concentration of relaxing imperfections, their annealing and migration activation energies are available from I = I(T) regularity processing. If the tested object is characterized with an energy gap, electrons and holes could be excited because of addition (to ultraviolet) radiation having and energy of the photons equal to the energy gap or a little bit higher than. This is the dual emission mode (DE) As the result the current of PE or PTSE is modulated. By this way the energy gap, excitation and decay time of a surface potential are available for estimation. The above emissions could be detected both from an entire surface of the tested object (integral mode) and locally (local mode). The measurements do not need any mechanical contacts to the tested object, that makes the technologies very gentle. The technique to detect emissions is preferably applied in high vacuum conditions. This could become a restriction for the objects that do not have vacuum resistance. Examples on the considered technologies to characterize semiconductor and insulator objects are provided.