Electron microscopy studies of semi-conducting materials

Boron (B) has the potential for generating an intermediate band in cubic silicon carbide(3C-SiC), turning this material into a highly efficient absorber for single-junction solarcells. The formation of a delocalized band demands high concentration of the foreignelement, but the precipitation behavior of B in the 3C polymorph of SiC is not wellknown. Here, probe-corrected scanning transmission electron microscopy (STEM) andsecondary-ion mass spectrometry are used to investigate precipitation mechanisms inB-implanted 3C- SiC as a function of temperature. Point-defect clustering was detectedafter annealing at 1273 K while stacking faults, B-rich precipitates and dislocationnetworks developed in the 1573 - 1773 K range.

The precipitates adopt therhombohedral B13C2 structure and trap B up to 1773 K. Above this temperature,higher solubility reduces precipitation and free B diffuses out of the implantation layer.Dopant concentrations of 1019 at.cm−3 were achieved at 1873 K. The concept of maximizing configurational entropy to enhance solid-state miscibilityinspires the exploration of unfamiliar composition spaces, and the popular, althoughimprecise, high-entropy (HE) designation seems destined to endure. The spotlight hasbeen on the mechanical properties of HE alloys, but interest in functional behavior isswiftly rising.

In particular, the vast potential of combining metal solid solutions withstructural main group elements to form HE semiconductor compounds is becomingevident. The structure of a (Zn,Mn)(Fe,Co,Ni)Sb compound is investigated by powderX-ray diffraction, STEM coupled to atomically resolved energy dispersive spectroscopy(EDS) and by energy-filtered convergent-beam electron diffraction (CBED). Distinctionbetween the 216 (half-Heusler) and 225 (full-Heusler) space groups is hindered by thesimilar scattering power of the transition metals in XRD. However, the structure couldbe deciphered by STEM/EDS with the space group further attested by CBED.