Twin-free and High-Quality DAST Crystals − Effected through Solutions of Lower Supersaturation Coupled with Isothermal Solvent Evaporation

Abstract

Growth of twin-free and high-quality 4-N,N-dimethylamino-4′-N′-methyl stilbazolium tosylate (DAST) crystals, with a surface roughness in the range of 1.7-3.8 nm (<4 nm) for as-grown crystals, has been achieved using solutions of lower supersaturation coupled with isothermal solvent evaporation. In addition, these efficient organic-ionic nonlinear optical (NLO) crystals possessed well-developed 001 and 001 h faces that facilitate direct utilization of these crystals for electrooptic (EO) and terahertz (THz) applications. Since this modified growth method necessitates a relatively lower amount (about 46%) of the expensive starting material as compared to that required for routine methods, it is also proven to be cost-effective.

Investigation on rapid growth of 4-N,N-dimethylamino-4′-N′-methylstilbazolium p-toluenesulphonate (DAST) crystals by SNM technique

“…During the growth period the solvent was completely evaporated and after 72 h crystal plates of size 4-6 Â 3-4 Â 0.1-1 mm 3 (Fig.1a) were harvested. Though there are reports on the growth of similar such thin plates of DAST, the growth processes adopted were complicated and also the growth period was relatively longer [16,23]. In the present work, we have demonstrated a simpler and cost effective method to grow DAST crystal plates of reasonably good quality in a very short period by careful control of concentration of the DAST-methanol solution coupled with faster evaporation.…”

“…The difficulties in growth positioning and nucleation are effectively solved by combining the slope nucleation method (SNM) with the Laser Irradiation Method (LIM) [15]. A cost effective method has been suggested by Brahadeeswaran et al [16] by using solutions of lower supersaturation coupled with isothermal solvent evaporation and this method facilitated the development of nearly parallel (0 0 1) and (0 0 1 ) faces so as to directly utilize the crystals for EO and THz applications.…”

“…Recently, the as-grown nonpolished DAST crystal was used successfully for THz generation by Taniuchi et al [19]. The rate of evaporation determines the size of crystals and the rapid evaporation favours the formation of a lot of tiny crystals [16]. Inspired with these facts, we have made an attempt to investigate the rapid growth of DAST crystals by slightly modifying the slope nucleation method and obtained reasonably good quality thin plates of DAST within 72 h. We have characterized the rapidly grown DAST crystals employing the powder XRD, FTIR, NMR, SEM, ac and dc conductivity and photoconductivity studies.…”

“…The smoothness of the surface and the size clearly suggest that this form of crystal can be useful for THz generation [30]. Interestingly, even in the case of DAST crystals grown with great care and optimized conditions, the formation of twins and hillocks are unavoidable [16,23]. However in the present study, we observe only one type of inclusions in the form of air bubbles, which were formed due to rapid evaporation and surprisingly the crystal is free from cracks even after undergoing rapid thermal stress and strain [31].…”

Studies on structure, growth and characterization of third order nonlinear optical 2-amino-5-chloropyridinium-4-amino benzoate single crystal

“…For example, extensive research has been conducted on 4-N,N-dimethylamino-4 -N -methyl-stilbazolium tosylate (DAST) crystals. The DAST single crystals were grown in a form of bulk or thin films to be used in nonlinear optical and electrooptic devices for creation and detection of terahertz (THz) frequencies [7,8]. Organic complexes, in which molecules having extremely improved electronic nonlinear optical polarization response possess conjugate systems, show several advantages over inorganic materials [6].…”