Synthesis, Characterization and Crystal Growth of I2-II-IV-VI4 and I4-II-IV2-VI7 Diamond-Like Semiconductors with potential In IR-NLO Applications

In this dissertation, several new and existing diamond-like semiconductors (DLSs) were synthesized and investigated for their potential in infrared nonlinear optical (IR-NLO) applications. In Chapter 2 growth of large single crystals of Li2MnGeS4 was carried out using iodine vapor transport and a newly created graphite-tube containment system. This crystallization method produced sizable single crystals on the scale of 2x1x1 mm3, that were used to determine the material’s magnetic properties. Magnetization data indicate that the compound is antiferromagnetic with a Néel temperature of 10 K and an effective magnetic moment of 5.6 /f.u.. The specific heat measurements show that as the field strength increases the Néel temperature decreases; the low Néel temperature confirms the weak magnetic coupling of the Mn2+ ions. Chapters 3, 4 and 5 report the new DLS Cu4MnGe2S7, Cu4CdSi2S7 and Li2ZnSiS4 for which detailed descriptions of their physical and electronic structures are given. Chapter 4 also reports the NLO properties of Cu4MnGe2S7 and Cu2MnGeS4. The chi(2) value for Cu4MnGe2S7 was determined to be 2.33 ± 0.86 pm/V. Due to the relatively weak SHG response, phase matching could only be tested up to 1600 nm, where the compound was found to be non-phase-matchable. On the other hand, Cu2MnGeS4 is phase matchable at 3100 nm and exhibits a significant chi(2) value of 16.9 ± 2.0 pm/V. Chapter 6 presents a study in which one polymorph of Cu2ZnSiS4 was targeted through alteration of the cooling rate. These products of these reactions were analyzed via neutron diffraction and solid-state MAS-NMR. While a single polymorph was not attained, a modified beta polymorph (gamma) was discovered