Growth of ultra-violet grade CaF2 crystals and their application for excimer laser optics

Mouchovski, Jordan; Haltakov, I.V.; Lyutskanov, Valentin

doi:10.1016/0022-0248(95)00949-3

Cited by 9 publications

(5 citation statements)

References 2 publications

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“…For small n, the distance between steps is comparable to or even smaller than the step height and the resulting surfaces are atomically flat. However, they can be considered as stepped surfaces with an extremely high density of steps, and the step formation energy can be calculated using equation (2). In the following we shall use the notation type I and type II for the steps on (n + 2, n + 2, n) and (n + 2, n, n) surfaces, respectively.…”

Section: Steps On the (111) Surfacementioning

confidence: 99%

“…Absorbing defects in the band gap are most relevant in the ultraviolet (UV) spectral region since, due to the high energy of UV photons, defects may induce linear absorption even in wide-band-gap materials. Among these, CaF 2 is one of the most notable ones, since it is a stable, chemically rather inert material that can be grown as a single crystal of high quality and combines a wide band gap of close to 12 eV with convenient optical properties [2]. Advanced polishing techniques allow surface processing of CaF 2 to highest optical quality [3] and, therefore, this material is a promising candidate for use in high-performance optical lens systems [4] for the next generation of UV laser steppers operated a wavelength of 193 nm [5].…”

Section: Introductionmentioning

confidence: 99%

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Theoretical modelling of steps on the CaF₂(111) surface

Puchin

Puchina

Huisinga

et al. 2001

J. Phys.: Condens. Matter

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The atomic and electronic structure and relaxation of the perfect (111) surface and several low-index surfaces of CaF2 are calculated using an ab initio Hartree-Fock method. We find marked differences between the bulk and surface valence band structures; however, the band gap is reduced by only 0.5 eV for the stepped surface. The (111) surface is found to exhibit no significant relaxation and we obtain a surface energy of 0.47 J m-2. The atomic structure of two types of stepped surface both having 0.32 nm high steps aligned along the [110] crystallographic direction is determined and the step energies are found to be 0.25 and 0.35 nJ m-1, respectively. Step energies for configurations involving other orientations of steps are considerably higher. The formation of double-height steps along [110], however, is found to be energetically favourable. A considerable amount of relaxation is found for stepped surfaces and we explain qualitatively why it results in a roughening of the surface in some cases. The energetic position of gap electronic states induced by steps on the (111) surface is found to be very similar to that for surface states of the perfect (111) surface; i.e. such states do not yield a significant density of states more than 0.5 eV above the bulk valence band maximum. We discuss how the step formation energies found here might explain surface topographical features found on cleaved and grown CaF2(111) surfaces.

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Section: Steps On the (111) Surfacementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Theoretical modelling of steps on the CaF₂(111) surface

Puchin

Puchina

Huisinga

et al. 2001

J. Phys.: Condens. Matter

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“…Fluorite-type crystals have been extensively investigated in the past [1][2][3][4][5][6][7][8] due to their broad technological relevance, including optical applications such as litho-excimer laser optics [9,10], beam deliveries, and zoom lenses, but also as a fluxing agent in the aluminum industry, as ceramic composites in fuel cell applications [11], and as an insulator within semiconductor multilayer structures [12]. Recently, CaF 2 nanoparticles have also attracted interest for medical applications, e.g., as markers in cancer therapy [13] and for potential use in dental care [14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Surface reconstruction of fluorites in vacuum and aqueous environment

Fisicaro

Sicher

Amsler

et al. 2017

Phys. Rev. Materials

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Surfaces and interfaces of bulk materials with liquids are of importance for a wide range of chemical processes.In this work, we systematically explore reconstructions on the (100) surface of calcium fluoride (CaF 2 ) and other fluorites (MF 2 ), M = {Sr,Cd,Ba} by sampling the configurational space with the minima hopping structure prediction method in conjunction with density functional theory calculations. We find a large variety of structures that are energetically very close to each other and are connected by very low barriers, resulting in a high mobility of the topmost surface anions. This high density of configurational states makes the CaF 2 (100) surface a very dynamic system. The majority of the surface reconstructions found in CaF 2 are also present in SrF 2 , CdF 2 , and BaF 2 . Furthermore, we investigate in detail the influence of these reconstructions on the crystal growth of CaF 2 in solvents by modeling the fluorite-water interface and its wetting properties. We perform a global structural search both by explicitly including water molecules and by employing a recently developed soft-sphere solvation model to simulate an implicit aqueous environment. The implicit approach correctly reproduces both our findings with the explicit-water model and the experimentally reported contact angles for the partial-hydrophobic (111) and hydrophilic (100) surfaces. Our simulations show that the high anion mobility and the low coordination of the (100) surface atoms strongly favors the adsorption of water molecules over the (111) surface. The aqueous environment makes terminations with low-coordination surface atoms more stable, promoting (100) growth instead of the (111).

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“…Taking into account that the relative error at estimating E l increases rapidly at wavelengths longer than 450 nm (see Ref. [74]), an optimum content of PbF 2 between 1.25 and 1.75 wt% can be cautiously inferred. Consequently, no matter how much PbF 2 is added (up to 2 wt.%) to the chemically purified fluorspar, the required purity of the starting material as regards oxygen contamination is not reached during its heating and melting, before the start of the melt crystallization despite the provision of HV conditions.…”

Section: Scavenger Efficiency Of Pbf 2 Without Htp Of Fluorsparmentioning

confidence: 99%

“…4) produced by a specially-designed [73,74] and optimized [68] technological scheme, called high-temperature purification (HTP), for the removal of the oxygen contaminants.…”

Section: Control Of Impurities In the Starting Materialsmentioning

confidence: 99%

Control of oxygen contamination during the growth of optical calcium fluoride and calcium strontium fluoride crystals

Mouhovski

2007

Progress in Crystal Growth and Characterization of Materials

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Growth of ultra-violet grade CaF2 crystals and their application for excimer laser optics

Cited by 9 publications

References 2 publications

Theoretical modelling of steps on the CaF₂(111) surface

Theoretical modelling of steps on the CaF₂(111) surface

Surface reconstruction of fluorites in vacuum and aqueous environment

Control of oxygen contamination during the growth of optical calcium fluoride and calcium strontium fluoride crystals

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Growth of ultra-violet grade CaF2 crystals and their application for excimer laser optics

Cited by 9 publications

References 2 publications

Theoretical modelling of steps on the CaF2(111) surface

Theoretical modelling of steps on the CaF2(111) surface

Surface reconstruction of fluorites in vacuum and aqueous environment

Control of oxygen contamination during the growth of optical calcium fluoride and calcium strontium fluoride crystals

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Product

Resources

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Theoretical modelling of steps on the CaF₂(111) surface

Theoretical modelling of steps on the CaF₂(111) surface