Growth Of Organic Single Crystal Research Articles

Wafer-Scale Epitaxial Growth of Two-dimensional Organic Semiconductor Single Crystals toward High-Performance Transistors.

The success of state-of-the-art electronics and optoelectronics relies heavily on the capability to fabricate semiconductor single-crystal wafers. However, the conventional epitaxial growth strategy for inorganic wafers is invalid for growing organic semiconductor single crystals due to the lack of lattice-matched epitaxial substrates and intricate nucleation behaviors, severely impeding the advancement of organic single-crystal electronics. Here, an anchored crystal-seed epitaxial growth method for wafer-scale growth of 2D organic semiconductor single crystals is developed for the first time. The crystal seed is firmly anchored on the viscous liquid surface, ensuring the steady epitaxial growth of organic single crystals from the crystal seed. The atomically flat liquid surface effectively eliminates the disturbance from substrate defects and greatly enhances the 2D growth of organic crystals. Using this approach, a wafer-scale few-layer bis(triethylsilythynyl)-anthradithphene (Dif-TES-ADT) single crystal is formed, yielding a breakthrough for organic field-effect transistors with a high reliable mobility up to 8.6 cm2 V-1 s-1 and an ultralow mobility variable coefficient of 8.9%. This work opens a new avenue to fabricate organic single-crystal wafers for high-performance organic electronics.

Unidirectional growth of organic single crystals of naphthalene, anthracene and pyrene by isothermal expansion of supercritical CO2.

Unidirectional single crystals without grain boundaries are highly important in optoelectronic applications. Conventional methods to obtain such crystals involve organic solvents or seed crystals, which have numerous drawbacks. We present here a supercritical CO2-mediated method of the single crystal formation of naphthalene, anthracene and pyrene on the (001) plane without using seed crystals. Single dominant peaks in powder XRD (PXRD) with low full width at half maxima (FWHM) are described. The dependency of crystal size on the rate of depressurization was measured by precise and isothermal expansion of scCO2 solutions. The experimental setup is illustrated for continuous preparation without emission of CO2 or discharge of material into the environment. The materials are shown to be fully converted into crystals indicating a rapid, scalable and environmentally benign process of single crystal formation with practically nil E factor.

Microspacing In-Air Sublimation Growth of Organic Crystals

Organic single crystals manifest the intrinsic physical properties of materials. However, traditional growth of organic single crystals is limited by low solubility from solutions or complexity from physical vapor deposition. Here we report a new method to grow organic single crystals by microspacing in-air sublimation, which avoids costly vacuum system and time-consuming procedures and is practical for a wide range of organic crystals. In situ crystal growth observation revealed an unprecedented vapor-to-melt-to-crystal mechanism, resulting from the micrometer scale spacing distance between the source and the growth position. FET devices based on the rubrene crystals directly grown on Si/SiO2 substrate exhibited higher mobility than the best record using SiO2 as the gate dielectric. This effective organic crystal growth technique can be affordable and handled for almost every lab, which may be beneficial for future research and application of organic crystals.

Growth of large naphthalene and anthracene single-crystal sheets at the liquid–air interface

The growth of organic single crystals of naphthalene (C10H8) and anthracene (С14H10) at the liquid‒air interface from a mixture of solvents has been investigated. The growth technique used in the study makes it possible to obtain single-crystal sheets up to 10 mm in size for 24 h. The surface morphology and structure of the crystals have been analyzed by optical microscopy and X-ray diffraction. C10H8 and С14H10 single crystals grow coplanarly along the (001) plane. A thermodynamic model of the flat-crystal nucleus formation at the liquid‒air interface, based on the analysis of the change in the free Gibbs energy, is considered.

Design and fabrication of eight zone vertical dynamic gradient freeze system for organic single crystal growth

Design and construction of the vertical dynamic gradient freeze (VDGF) system operating in the temperature range from 50 °C to 500 °C for growing organic single crystals are described. The design of VDGF system consists of furnace, control system, translation assembly, and image capturing device. Furnace has been constructed with eight zones controlled independently by a dynamic temperature control system for achieving desired thermal environment and multiple temperature gradients, which are essential for the growth of organic single crystals. The transparent furnace enables direct observation to record and monitor the solid-liquid interface and growth of crystals through charge coupled device based video camera. The system is fully computerized hence it is possible to retrieve the complete growth and furnace history. In order to investigate the functioning of the constructed VDGF system for the growth of organic single crystals, a well known organic nonlinear optical single crystal of benzimidazole was grown. The crystalline quality and the optical transmittance of the grown crystal were studied.

Development of compact CW-IR laser deposition system for high-throughput growth of organic single crystals

We developed a compact continuous-wave infrared (CW-IR) laser deposition system for the high-throughput growth of organic single crystals. In this system, two CW-IR lasers are used for the sample heating and thermal evaporation of materials. The CW-IR laser heating is simple and allows good control of the deposition rate and growth temperature, in response to the on/off laser switching. Six samples can be loaded simultaneously in a chamber, which allows one-by-one sequential deposition for high-throughput experiments, without breaking the vacuum. Using this setup, we studied the effect of ionic liquids on the growth of C60 crystals in vacuum.

Growth and characterization of an organic NLO crystal:4-chloro- 4-methyl benzylidene aniline

In this paper, we report for the first time the synthesis, growth and characterization of a new organic NLO single crystal of 4 choloro-4-methyl benzylidene aniline. The title compound is synthesized and single crystals were grown by the slow evaporation technique at constant temperature. The grown single crystals have been characterized by single crystal XRD; powder XRD, FTIR, NMR, UV-Vis, thermal analysis and microhardness studies. From the XRD study, it is found that the crystals are in the monoclinic system. The FTIR spectrum was recorded to identify the various functional groups present in the group compound. The formation of the product was confirmed from NMR spectral analysis. The optical transparency was determined by UV-visible spectroscopy. The melting point is found to be 108°C from the DSC curve. The second harmonic generation (SHG) efficiency of the crystal was obtained using ND-YAG laser which is found to be 7.5 times that of KDP.

Growth of Single-Crystal Phase Pentacene in Ionic Liquids by Vacuum Deposition

Here, we propose a new vacuum deposition process with an ionic liquid, and demonstrate that the single-crystal phase of pentacene, which is thermodynamically the most stable phase of its polymorphs, can be easily grown through this process. In this process, pentacene was deposited at a temperature above 363 K directly into an ionic-liquid droplet that had been prepared on a substrate beforehand, and nucleated in the ionic-liquid droplet to form many plate-shape crystals in the single-crystal phase. Even though our process time was just 100 min, the crystal quality of pentacene single-crystal phase, the maximum size of which was as large as 300 μm, was almost equivalent to that obtained by the conventional solution growth process. The ionic-liquid assisted vacuum deposition, therefore, will become one of the alternative processes for the growth of organic single crystals in vacuum.

Direct Observation of Gas Phase Nucleation during Physical Vapor Transport Growth of Organic Single Crystals Using a Transparent Furnace

We observed the physical vapor transport growth of tetracene (C18H12) using a transparent furnace. We found that free-standing small crystals are formed in the gas flow and sometimes stick on the solid surface and become the seeds for larger crystals. A theoretically predicted convection was observed by tracking the trajectory of flowing crystal particles.

Growth of organic single crystals by transparent vertical Bridgman technique and its characterization

In order to grow benzophenone single crystal, an organic nonlinear optical material, a cost-effective Vertical Bridgman–Stockbarger system has been designed and fabricated by employing a two-zone, transparent furnace made out of immiscible liquids. Transparent, optical quality benzophenone single crystals were successfully grown as a result of a suitable thermal gradient achieved by means of introducing an intermediate liquid in between the two immiscible liquids. The effect of change in the volume of the intermediate liquid, thereby the thermal gradient on the growth parameters, was analyzed. The quality of the grown single crystal was justified using X-ray powder diffraction analysis, FTIR, TG-DTA and optical transmission studies.

Modified floating-zone growth of organic single crystals

For organic materials floating-zone crystal growth is superior to other melt growth processes in two significant respects: (1) the absence of crucible-induced mechanical damage and (2) minimum heating-induced chemical degradation. Due to the rather low surface tension of organic melts, however, floating-zone crystal growth under normal gravity has not been possible so far but microgravity is ideal for such a purpose. With the help of a modified floating-zone technique, organic single crystals of small cross-sections were test grown first under normal gravity. These small crystals were round and rectangular single crystals of benzil and salol, up to about 7 cm long and 6 mm in diameter or 9 mm × 3 mm in cross-section.

The Growth of Organic Single Crystals in Glass Capillaries for Second Harmonic Generation

ABSTRACTThe growth and characterisation of a number of organic single crystals, e.g. benzil, 2–methyl–4– nitroaniline and 2–N,N–dimethylamino–5–nitroacetanilide, in silica capillary has become fairly well established over recent years. [1–6 ] However the growth of these same compounds in glass capillary with a much higher refractive index than silica has received little interest. Crystal cored fibres, ccf's, in which there is a close match of the refractive index of the cladding to that of the core allows the possibility of fabricating single mode waveguides with useful dimensions for crystal growth. There is a better overlap integral between phase matched fundamental and second harmonic modes in a low moded structure than in a structure with more allowable modes and thus a rise in the conversion efficiency can be expected if the correct dimensions of waveguide are chosen. If a ccf of high conversion efficiency, 10% at 0.1 mW average power, could be made then the promise of fabricating an organic optical nonlinear device, e.g. parametric amplifier, might be realised. In this paper we will describe how the growth method adopted for silica clad organic crystals has been adapted for their growth in a range of Schott glasses which are better matched in refractive index, RI, than silica to the organic material. The linear and nonlinear optical properties of these crystal cored fibres will be given in terms of; the orientation of the crystal axes with respect to the fibre direction; the sideways scattering characteristics from defects; the throughput of the fundamental beam; the polarisation states of both the fundamental and the second harmonic outputs; and the overall efficiency of second harmonic generation.