Developments in Measuring and Calculating Chemical Vapor Transport Phenomena Demonstrated on Cr, Mo, W, and Their Compounds

Lenz, M.; Gruehn, R.

doi:10.1021/cr940313a

Cited by 58 publications

(46 citation statements)

References 416 publications

(802 reference statements)

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“…The well-established underlying mechanism is the formation of a volatile mono-hydroxide at elevated temperatures by a reversible reaction [21,28]. In thermodynamic equilibrium the reaction reads…”

confidence: 99%

The important role of water in growth of monolayer transition metal dichalcogenides

et al. 2017

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The important role of water in growth of monolayer transition metal dichalcogenides Interest in transition metal dichalcogenides (TMDs) has been renewed by the discovery of emergent properties when reduced to single, two-dimensional (2D) layers. The transition to direct band gap [1,2], emerging charge density waves [3,4], high mobility [5][6][7], and valley polarization [8][9][10] are some of the many exciting properties that have been reported in the TMD literature recently. A major bottleneck to this research is the lack of reproducible and large scale synthetic methods for high quality, consistent monolayer TMD samples. The dominant growth method is the vaporization and subsequent chalcogenization of solid metal oxides in the presence of gaseous chalcogen precursors. This process is commonly referred to as chemical vapor deposition (CVD) or powder vaporization [11][12][13][14]. Due to its simplicity, CVD is extensively used by the TMD community to produce high quality, micron-sized single crystals [11][12][13][15][16][17][18][19]. Understanding the vaporization chemistry of solid transition metal precursors and vapor transport of volatilized precursors, particularly with respect to the influence of water vapor, is critical. Humidity, i.e. water content of the reaction environment, is an important parameter in the gas phase synthesis of inorganic materials, and while it is typically thought of as a contaminant, water is also an effective transport agent [20][21][22][23]. In this communication, we describe the synthesis of luminescent monolayer TMD islands by introducing water vapor as a simple means of controlling the volatilization and transport of the metal oxide precursor. Our experiments demonstrate a direct correlation between gas phase water content and the morphology of the resulting films. In particular, explicit control of the in situ water vapor concentration allows us to switch between two modes of growth: one in an effectively dry environment, in which the transition metal oxide source is converted directly to TMD material through a solid state reaction with the chalcogen source, and another in which the transition metal oxide undergoes vapor transport followed by reaction with the chalcogen source. We show that a small amount of water enhances the volatilization, and hence vapor transport, of the oxides of tungsten and molybdenum at the elevated temperatures (500-800 °C) used in the conversion or growth of their TMD counterparts. We attribute this effect to the enhanced vaporization of WO 3 and MoO 3 in the presence of water, first demonstrated in the 1930s and Our results show a direct correlation between gas phase water content and the morphology of TMD films. In particular, we show that the presence of water enhances volatilization, and therefore the vapor transport of tungsten and molybdenum oxide. Surprisingly, we find that water not only plays an important role in volatilization but is also compatible with TMD growth. In fact, carefully controlled humidity can consistently produce high qual...

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confidence: 99%

The important role of water in growth of monolayer transition metal dichalcogenides

et al. 2017

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“…The importance of fluid dynamics in determining the right growth conditions in such systems is well described by the literature [22][23][24][25][26][27][28][29][30][31][32]. The CVT crystal grower will often encounter dimensionless numbers such as the Grashof, Schmidt, Prandtl and Rayleigh numbers that serve for the description of the system, especially with regard to diffusion and convection.…”

Section: Introductionmentioning

confidence: 99%

Crystal growth of Cu2ZnSnS4 solar cell absorber by chemical vapor transport with I2

Colombara

Delsante

Borzone

et al. 2013

Journal of Crystal Growth

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Single crystals of Cu 2 ZnSnS 4 have been produced within sealed quartz ampoules via the chemical vapour transport technique using I 2 as the transporting agent. The effects of temperature gradient and I 2 load on the crystal habit and composition are considered. Crystals have been analysed with XRD, SEM, and TEM for compositional and structural uniformities at both microscopic and nanoscopic levels. The synthesized crystals have suitable (I 2 -load dependent) properties and are useful for further solar absorber structural and physical characterizations. A new chemical vapour transport method based on longitudinally isothermal treatments is attempted. Based on a proposed simplistic mechanism of crystal growth, conditions for crystal enlargement with the new method are envisaged.

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Section: Methodsmentioning

confidence: 99%

“…In order to verify the calculations, chemical vapour transport was performed at various source temperatures and temperature gradients by using a transport balance [34], which permits in situ measurements of the mass flow by time. Figure 5 shows the experimental mass flow for Sb 2 Se 3 , Sb 2 Te 3 , Bi 2 Se 3 , and Bi 2 Te 3 under similar transport conditions of ϑ source = 500 °C, and ∆T = 50 K. Basically transports are feasible for all M 2 Q 3 compounds (M = Sb, Bi, Q = Se, Te) with the sink temperature above 450 °C.…”

Section: Transport Experimentsmentioning

confidence: 99%

Chemical Vapour Transport of Bismuth and Antimony Chalcogenides M₂Q₃ (M = Sb, Bi, Q = Se, Te)

Schöneich¹,

Schmidt

Schmidt³

2010

Zeitschrift anorg allge chemie

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Abstract. Thermodynamic modelling of the ternary systems M/Q/I (M = Sb, Bi, Q = Se, Te) indicated solid-gas equilibria suitable for chemical vapour transport of bismuth and antimony chalcogenides. The predictions of the modelling were confirmed by transport experiments on a transport balance. The optimum transport conditions using iodine as transport agent were determined for all systems to: ϑ source = 500 °C and ϑ sink = 450 °C. For ∆T > 50 K the sequential transport of chalcogenide iodides MQI followed by M 2 Q 3 occurs. Thermodynamic standard data of the gas species SbI(g) were concluded from equilibrium calculations: ∆H

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Developments in Measuring and Calculating Chemical Vapor Transport Phenomena Demonstrated on Cr, Mo, W, and Their Compounds

Cited by 58 publications

References 416 publications

The important role of water in growth of monolayer transition metal dichalcogenides

The important role of water in growth of monolayer transition metal dichalcogenides

Crystal growth of Cu2ZnSnS4 solar cell absorber by chemical vapor transport with I2

Chemical Vapour Transport of Bismuth and Antimony Chalcogenides M₂Q₃ (M = Sb, Bi, Q = Se, Te)

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Developments in Measuring and Calculating Chemical Vapor Transport Phenomena Demonstrated on Cr, Mo, W, and Their Compounds

Cited by 58 publications

References 416 publications

The important role of water in growth of monolayer transition metal dichalcogenides

The important role of water in growth of monolayer transition metal dichalcogenides

Crystal growth of Cu2ZnSnS4 solar cell absorber by chemical vapor transport with I2

Chemical Vapour Transport of Bismuth and Antimony Chalcogenides M2Q3 (M = Sb, Bi, Q = Se, Te)

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Chemical Vapour Transport of Bismuth and Antimony Chalcogenides M₂Q₃ (M = Sb, Bi, Q = Se, Te)