Closed-tube chemical-transport mechanisms in the Cd:Te:H:Cl:N system

Paorici, C.; Pelosi, C.; Attolini, G.; Zuccalli, G.

doi:10.1016/0022-0248(75)90072-x

Cited by 20 publications

(10 citation statements)

References 13 publications

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“…Apart from pressure, reactor design can also influence the transport process and thus the reaction kinetics. Taking the typical ampoule reactor as an example, ampoules with a small diameter usually favor diffusion but not convection controlled transport, resulting in a slow reaction rate . Collectively, in practical applications, the kinetics of CVT reactions can be modulated by tuning factors that influence the transport process of the reaction.…”

Section: Fundamentals Of Cvt Reactionsmentioning

confidence: 99%

Chemical Vapor Transport Reactions for Synthesizing Layered Materials and Their 2D Counterparts

Wang

Luo

Lü

et al. 2019

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semimetals (Si and Ge) to transition metal dichalcogenides (TMDs), which can be tuned from semiconductors to superconductors, have been intensively investigated. [8] Despite the recent advances in 2D materials, it is still challenging to obtain 2D materials with desired layers and size in facile and controllable manners.Indeed, continuous research has been carried out on the synthesis of 2D materials. [9] Generally, two synthetic strategies, known as top-down and bottom-up, are applied to obtain 2D materials. In the common top-down strategy, 2D materials are exfoliated from their bulk counterparts. Differently, using the bottom-up strategy, 2D materials with a few thin layers, even an atomically thin layer, can be directly synthesized from small building blocks such as molecules and atoms. [10] In these synthetic strategies for 2D materials, chemical vapor transport (CVT) reaction, an old yet powerful technology, plays an important role because CVT reactions can be used for both topdown and bottom-up syntheses of 2D materials. [11] CVT reactions represent a category of reactions with one common feature: a condensed phase, typically a solid, sublimes in the presence of a gaseous reactant (the mineralizer), and then deposits elsewhere usually in the form of crystals. [12] Notably, CVT is different from chemical vapor deposition (CVD), another chemical vapor-based approach for synthesizing 2D materials. Specifically, the main difference between CVT and CVD lies in the source materials for synthesizing products, where solid reactants are typically used in CVT and gaseous precursors are usually applied in CVD. The difference induces consequent differences in reactor design, operational control, and product features, thus bringing strengths and drawbacks for each approach. Since the discovery of CVT reaction by Bunsen in 1851, comprehensive understanding of CVT reactions in both experimental exploration and theoretical modeling has been established. [13] Furthermore, thousands of CVT reactions have been applied till now, producing a great variety of pure and crystalline solids, including metals, metalloids, intermetallic phases, metal oxides, halides, chalcogen halides, chalcogenides, and pnictides. [13,14] The knowledge about CVT reactions, together with the large number of applicable reactions, can offer opportunities for the controllable synthesis of 2D materials and the exploration of new 2D materials. Unfortunately, for the preparation of 2D materials, in stark contrast to the wide application of CVD, 2D materials, namely thin layers of layered materials, are attracting much attention because of their unique electronic, optical, thermal, and catalytic properties for wide applications. To advance both the fundamental studies and further practical applications, the scalable and controlled synthesis of large-sized 2D materials is desired, while there still lacks ideal approaches. Alternatively, the chemical vapor transport reaction is an old but powerful technique, and is recently adopted for synthesizing 2D material...

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Section: Fundamentals Of Cvt Reactionsmentioning

confidence: 99%

Chemical Vapor Transport Reactions for Synthesizing Layered Materials and Their 2D Counterparts

Wang

Luo

Lü

et al. 2019

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“…This is the case of FeS [68] with FeCl 2 as transport agent, or the case of TeO 2 when transported with TeCl 4 [69]. However, cases in which the transport agent is a compound with no common ion with the substance to be transported have also been reported, for instance the transport of CdTe with NH 4 Cl [70].…”

Section: Cvt Growth Techniquesmentioning

confidence: 97%

“…The number of condensed phases may not be the same in the two regions. An example is given by the CdTe/ NH 4 Cl system [70] where, at sufficiently low total pressure and temperature (T450 C), two condensed phases form at T(0): CdTe(s) and Te(l).…”

Section: Cvt Growth Techniquesmentioning

confidence: 99%

Vapour growth of bulk crystals by PVT and CVT

Paorici

Attolini

2004

Progress in Crystal Growth and Characterization of Materials

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“…These values are listed [33] or can be deduced using a simple estimation from listed values [34]. If we use the Lennard-Jones potential to approximate the intermolecular potential field, Ω ij is obtained as a dimensionless function of reduced temperature [33] * ij…”

Section: Theoretical Modelmentioning

confidence: 99%

“…At the growth temperature we have the following gaseous species that contains compositional fractions of the initial amount of iodine: I 2 and ZnI 2 . Starting from the metallic iodine quantity introduced in the ampoule before being sealed off under vacuum and applying the law of the perfect gases for everyone of these gaseous components occupying the volume V of the ampoule, Paorici [34,37] has established a correlation between the initial iodine concentration and the partial pressures of the gaseous compounds containing iodine, given by the relation: where: c is the initial concentration of iodine , i I ν are the stoichiometric coefficients of the iodine atoms in the gaseous specie "i" (i=I 2 , ZnI 2 ), p i (bar) is the partial pressure of the gaseous specie "i", R is the perfect gases constant, T is the average absolute temperature and M I is the molar mass of iodine. To calculate the partial pressures of all the gaseous components (Se 2 , I 2 , ZnI 2 ) we have used the above eq.…”

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Kinetical study of the nonstoichiometric vapour growth process in the system ZnSe:I₂

Stănculescu

2010

Cryst. Res. Technol.

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We have studied the growth of ZnSe crystals by chemical transport in a closed system in nonstoichiometric conditions, and we have deduced that the interface kinetics is the phenomenon limiting the growth process. The effect on the growth process of the deviation from stoichiometry of the II-VI compound was investigated using a mathematical model that involves indirect data computed from directly obtained experimental values. The experimental crystallization rate was compared with the maximum value of the transport flux calculated using the Arizumi-Nishinaga model. The influence of the stoichiometry of the source material and of the variations in the growth parameters (supercooling, geometrical dimension, specific loading of the ampoule and iodine concentration) on the ZnSe crystal growth process has also been studied. IntroductionThe growth of the bulk wide gap II-VI semiconductor compounds, such as zinc selenide (ZnSe) for optical and opto-electronic applications, rises problems because they have high melting points and they decompose in volatile components below this temperature. Alternative methods for the crystals growth are the growth from the vapour phase by physical transport [1][2][3] or chemical transport in a closed system using different transport agents (iodine [4][5][6][7][8][9][10][11][12][13][14], NH 4 Cl [15], Zn(NH 4 ) 3 Cl 5 [16][17][18]). In the last system the growth rate is controlled either by the interface kinetical processes or by the mass transport in the vapour phase [19]. The first thermodynamic analysis of the chemical transport reaction in closed tube system has been done by Schäfer [20][21][22] who explained the transport of the solid material considering only the diffusion and laminar flows and neglecting all the other influences on the transport in the vapour phase. Lever [23] has developed a model for the transport of the solid between two regions situated at different temperatures and he has deduced a transport function for an one-dimensional, steady-state diffusion limited process, in a single heterogeneous equilibrium system. Arizumi-Nishinaga [24][25][26] has introduced another transport function taking into account equilibrium considerations, Fick's diffusion law and Schäfer expression for the transport rate.The method to grow single crystals from the vapour phase by chemical transport was firstly presented by Nitsche [27] and further developed by Kaldis [28]. Lately the interest for this growth method has increased and computational studies of different systems such as ZnSe+I 2 have been developed [12][13][14].This paper presents some results about the influence of the stoichiometry of the starting material on the crystallization process. To investigate the effect of the deviation from stoichiometry and thermal regime on the growth process of ZnSe crystals by iodine transport, we have considered two different successive phenomena: the transport of the species present in the gaseous phase (transport kinetics) and the incorporation of the gaseous species at the crystal-vapou...

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Closed-tube chemical-transport mechanisms in the Cd:Te:H:Cl:N system

Cited by 20 publications

References 13 publications

Chemical Vapor Transport Reactions for Synthesizing Layered Materials and Their 2D Counterparts

Chemical Vapor Transport Reactions for Synthesizing Layered Materials and Their 2D Counterparts

Vapour growth of bulk crystals by PVT and CVT

Kinetical study of the nonstoichiometric vapour growth process in the system ZnSe:I₂

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Closed-tube chemical-transport mechanisms in the Cd:Te:H:Cl:N system

Cited by 20 publications

References 13 publications

Chemical Vapor Transport Reactions for Synthesizing Layered Materials and Their 2D Counterparts

Chemical Vapor Transport Reactions for Synthesizing Layered Materials and Their 2D Counterparts

Vapour growth of bulk crystals by PVT and CVT

Kinetical study of the nonstoichiometric vapour growth process in the system ZnSe:I2

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Product

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Kinetical study of the nonstoichiometric vapour growth process in the system ZnSe:I₂