Polarization-sensitive second harmonic generation microscopy of α-quartz like GeO₂ (α-GeO₂) polycrystal

Spherulitic crystallization of quartz-like GeO2 and correlated second harmonic generation in sodium tantalum germanate glasses

“…when the diameter of the spherulite is perpendicular to the incident laser polarization. According to the quartz-like α-GeO2 (D3 point group) which crystalline structure is set as a positive uniaxial trigonal crystal, having a space group P3121 or P3221 [38], [51], both E Raman modes and the most intense χ (2) coefficients are expected for an excitation perpendicular to the trigonal c axis [49]. Thus, both Raman and SHG data are in agreement with the D3 point group of α-GeO2 and one can deduce form the correlative maps in Table 4 a spatial distribution of the crystallites which tends to be radial with the spherulite growth.…”

“…Finally, symmetry aspects explain those optical responses. For example germanium oxide GeO2 can be present as a glassy material as well as crystalline phases quartz (α-GeO2 trigonal, P3121, P3221) or rutile (r-GeO2 tetragonal, P42/mnm) and the final second order NLO response associated with specific anisotropy of each structure [38].…”

Growth of small GeO2 single crystals on a polyvinyl chloride substrate at room temperature using oversaturate aqueous solution

“…For this reason, germanium is now being reconsidered as a next‐generation material for electronic devices, while chemical characteristics and usage of germanium dioxide are gaining importance in design of advanced electronic devices . Germanium dioxide can take crystal structure of α‐quartz type or cristobalite type, while likely taking amorphous form; though it resembles silicon dioxide, a number of distinctions are known including water solubility and organic polymerization catalytic activity . Germanium dioxide is reported to be water soluble but the solubility value is estimated differently …”

“…4 Germanium dioxide can take crystal structure ofquartz type or cristobalite type, while likely taking amorphous form; though it resembles silicon dioxide, a number of distinctions are known including water solubility and organic polymerization catalytic activity. [5][6][7] Germanium dioxide is reported to be water soluble but the solubility value is estimated differently. [7][8][9][10] We prepared homogeneous aqueous solutions of multiple metal elements including germanium, and developed low-temperature processes to synthesize complex germanates from such solutions.…”