Monocrystal Growth

Demianecz L.N. Hydrothermal synthesis of transition metal oxides. In Hydrothermal Synthesis and Monocrystal Growth. Moskva Nauka, 1982 4-26. 

Special crystallization processes such as zone melting, monocrystal growth, high-pressure crystallization and crystallization by transfer reaction are not discussed here. Introductory literature, for example, is given in [0.4 and 7.1]). 

The achievement of the corresponding monocrystals of sufficient optical and crystalline quality is made possible only after very thorough purification. Chemical impurities are known to disturb the crystal lattice through the occurence of twins, veils dislocations, rounding-off of faces ultimately quenching further growth. Any crystalline defect dramatically increases the residual absorption coefficient and lowers the optical damage threshold. 

Characterization. It is both important for crystal growth and for checking the purification of materials. It takes place at every stage, from synthesis to the monocrystal. There are two aspects the control of material purity before crystal growth and the control of the crystalline quality of raonocrystals. 

Figure 4. Examples of low-temperature limit of rate constant of solid-state chamical reactions obtained in different laboratories of the USSR, United States, Canada, and Japan (1) formaldehyde polymerization chain growth (USSR, 1973 [56]) (2) reduction of coordination Fe-CO bond in heme group of mioglobin broken by laser pulse (United States, 1975 [65]) (3) H-atom transfer between neighboring radical pairs in y-irradiated dimethylglyoxime crystal (Japan, 1977, [72], (4, 5) H-atom abstraction by methyl radicals from neighboring molecules of glassy methanol matrix (4) and ethanol matrix (5) (Canada, United States, 1977 [11, 78]) (6) H-atom transfer under sterically hampered isomerization of aryl radicals (United States, 1978 [73]) (7) C-C bond formation in cyclopentadienyl biradicals (United States, 1979 [111]) (8) chain hydrobromination of ethylene (USSR, 1978 [119]) (9) chain chlorination of ethylene (USSR, 1986 [122]) (10) organic radical chlorination by molecular chlorine (USSR, 1980 [124,125]) (11) photochemical transfer of H atoms in doped monocrystals of fluorene (B. Prass, Y. P. Colpa, and D. Stehlik, J. Chem. Phys., in press.).

Dendritic deposits grow under mass transport-controlled electrodeposition conditions. These conditions involve low concentration of electrolyte and high current density. A dendrite is a skeleton of a monocrystal consisting of stem and branches. The shapes of the dendrites are mainly determined by the directions of preferred growth in the lattice. The simplest dendrites consist of the stem and primary branches. The primary branches may develop secondary and tertiary branches. The angles between the stem and the branches, or between different branches, assume certain definite values in accordance with the space lattice. Thus, dendrites can be two dimensional (2D) or three dimensional (3D). 

Chen XH, et al. Direct growth of hydroxy cupric phosphate heptahydrate monocrystal with honeycomb-like porous structures on copper surface mimicking lotus leaf. Cryst Growth Des 2009 9(6) 2656-61. 

RM Leonhardt, L Peichl. Growth of tantalum carbide monocrystals. J Cryst Growth 54 223, 1981. 

Moreover, because of the constraints, it is not very probable that, even on the basis of a monocrystal of A, a monociystal of B can be obtained but rather a multitude of crystals in a more or less disordered arrangement. To take into accoimt the whole of the phenomenon, models of total growth have been established. 

As the droplets are constantly fed by the gas phase transfer, precipitation continues with the growth of SiC monocrystals along the crystaUographic direction (111). The morphology varies with the composition of the gas phase. For low pressures of SiO, whiskers with circular cross-section (0 < 5 pm - L = mm) with a perfectly smooth surface can be manufactured. 

For thicker films of NiO formed at higher temperatures (e.g. 600°C), ex-situ RHEED is useful to examine the structure of the oxide which forms [7]. Figure 4.2 compares the oxidation of electropolished (112), (111) and (100) monocrystals with electropolished polycrystaUine nickel at 600°C. Only -lOiim of oxide has formed on (112)Ni after 1 h from RHEED, the single orientation prior oxide [(111) antiparallel NiO on (111) steps of the (112) macrosurface] persists during oxidation. The lower growth rate is the result of formation of oxide by lattice diffusion only. The increased rate of oxidation... 

---