We present a comprehensive three-dimensional analysis of Kelvin probe force microscopy of semiconductors. It is shown that high-resolution electronic defect imaging is strongly affected by free carrier electrostatic screening, and the finite size of the measuring tip. In measurements conducted under ambient conditions, defects that are not more then $2\text{nanometers}$ below the surface, and are at least $50\text{nanometers}$ apart can be imaged only if the tip-sample distance is not larger then $10\text{nanometers}$. Under ultrahigh vacuum conditions, when the tip-sample distance can be as small as $1\text{nanometer}$, it is shown that the tip-induced band bending is only around a few millivolts, and can be neglected for most practical purposes. Our model is compared to ultrahigh vacuum Kelvin probe force microscopy measurements of surface steps on GaP, and it is shown that it can be used to obtain local surface charge densities.

Development of efficient, inexpensive, and environmentally-friendly light emitters, particularly devices that produce white light, have drawn intense interest due to diverse applications in the lighting industry, photonics, solar energy, and others. We present a simple strategy for the fabrication of flexible transparent films exhibiting tuneable light emission through one-pot synthesis of polymer matrixes with embedded carbon dots assembled in situ. Importantly, different luminescence colours were produced simply by preparing C-dot/polymer films using carbon precursors that yielded C-dots exhibiting distinct fluorescence emission profiles. Furthermore, mixtures of C-dot precursors could be also employed for fabricating films exhibiting different colours. In particular, we successfully produced films emitting white light with attractive properties (i.e. “warm” white light with a high colour rendering index) – a highly sought after goal in optical technologies.