Growth of germanium crystals by time-varying temperature profile, CVT methods

• Germanium crystals grown by chemical vapour transport (CVT) technique. • Use of different CVT thermal profiles: stationary vs time-varying thermal profiles. • Increase in the size of germanium crystals. Germanium crystals have been prepared by Chemical Vapour Transport (CVT) to study the influence of the thermal profile on the crystal growth: using the stationary temperature profile, the Linear Time-varying Temperature Profile (LTVTP) and the LTVTP followed by the oscillatory temperature profile in the same run. With the optimization of the growth parameters we have obtained a progressive increase of the crystal sizes and a reduction of the crystalline nuclei during the primary nucleation. The final result was only one crystal grown using the LTVTP associated with oscillatory temperature profile. The crystals morphology observed by scanning electron microscopy showed details of their shape typical of germanium, the cubic structure was confirmed by X-ray diffraction.