Effet de la structure sur les propriétés optiques de couches minces de composés de tungstène obtenues par décomposition en phase vapeur: Influence sur la sélectivité spectrale

Yous, B.; Robin, Stéphane; Robin, Jean Jacques; Donnadieu, A.

doi:10.1016/0040-6090(85)90350-5

Cited by 12 publications

(3 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Table IV presents a summary of data for W films deposited under the three different vacuum conditions. Surface compositions are spatially homogeneous and, in the case of HV/vac and HV/air films, roughly consistent with less than one CO group per W. The Auger line shapes for carbon shown in Figures [12][13][14] indicate that it is primarily graphitic or amorphous on LV/air films but possibly a mixture of graphitic or amorphous and carbidic on high-vacuum-deposited films.30 This surface layer, which is not appreciably air sensitive, is probably formed by surface reactions after irradiation is complete. It is removed by 1-3 min of sputtering, indicating that its thickness is of the order of 50 A. Off-spot material is also observed for W films; however, it MW/cm2 beam for 5 s. Three sputter depths are shown.…”

Section: Methodsmentioning

confidence: 68%

“…Although tungsten oxides, like molybdenum, reduce under ion bombardment, the rapid decrease in oxygen signal during the first 1-3 min of sputtering indicates that the lade of measurable contamination is not an artifact. The survey data (Figures [12][13][14] show clearly that, unlike Mo and Cr, the W film centers and edges have the same compositions. Linescan data presented in Figure 15 confirm the absence of C and O throughout the film.…”

Section: Methodsmentioning

confidence: 94%

“…14 indicate that it is primarily graphitic or amorphous on LV/air films but H b l y a mixave of graphitic or amorphous and carbidic on h i g h -v a c u w t e d f h . m Thhs surface layer, which is not appreciably air Sensitive, is pmbably formed by surface reactions after irradiation is complete.…”

mentioning

confidence: 96%

See 2 more Smart Citations

Visible laser-induced nucleation and growth of chromium, molybdenum, and tungsten films from the hexacarbonyls: reactivity of carbon monoxide on film surfaces

Houle¹,

Singmaster²

1992

J. Phys. Chem.

View full text Add to dashboard Cite

Continuous visible laser irradiation is used to deposit Cr, Mo, and W films from the hexacarbonyls by thermal excitation.Detailed analyses of the films by scanning Auger microscopy show that the Mo and Cr films are spatially inhomogeneous, having clean metal centers surrounded by contaminated metal rings. W films are completely pure. Depth profiles reveal that, prior to formation of clean Mo and Cr, an interfacial layer of contaminated material is deposited which becomes progreesively metal rich as thickness increases. If such a layer is formed for W, it is very thin. The measured composition profiles are compared to calculated surface temperature distributions in order to extract information on the kinetics of CO dissociation and desorption during growth. The temperature and mechanism simulations show that CO desorption dominates above about 450 K, ensuring that pure metal is deposited. Below that temperature contamination occurs. Previous investigations of film growth from metal hexacarbonyls have led to the conclusion that film purity will only be high at temperatures exceeding 800 K, where recombinative desorption of CO is fast. The origins of the large discrepancy in temperatures are discussed.Chemical processes leading to growth of metal oxycarbide material at the fdm edges and film-substrate interface are explored using data from the catalysis literature. The strong parallels found between the laserdeposited material and supported catalysts formed from the hexacarbonyls suggest that the oxycarbide films may have significant Lewis acid-base character, leading to faster CO and metal40 bond dissociation rates. Thus, formation of contaminated material appears to depend on local surface composition as well as temperature. Iatroduction, The identification of useful gas-phase precursors for laser-ind u d chemical vapor deposition (LCVD) of the early transition metals Cr, Mo, and W has been a surprisingly inactive area. Since the process uses a laser beam to heat a localized area of the substrate and c a w pyrolytic decomposition of incident molecules, the few precursor systems which have been studied arc those used previously in conventional chemical vapor deposition (CVD) procarpes. By far, the major effort has bem applied to continuous laser deposition from the hexacarbonyl'" and hexafluoride7 of tungsten, with some limited attention to molybdenum hexacarbonyl>8 chromium he~acarbonyl?.~ and the bis(benzene) complexes of Cr and Mo.l0 Film characterization and processhas been on rapid direct writing of small features. It has been shown that film resistivities of Mo and W approach those of bulk material as laser power, and thus surface temperatures, increase.6 The lowest resistivity reported for W, approximately 1-2 times the bulk value for a-tungsten, is obtained using a 355-nm Ar+ laser beam to deposit lines on glass in a cell heated to 360 K.6Surface temperatures are estimated to be 800-1000 K during growth. Although ultraviolet light is used, the photolysis yield of the hexacarbonyls at that wavelength is so s...

show abstract

Section: Methodsmentioning

confidence: 68%

Section: Methodsmentioning

confidence: 94%

See 1 more Smart Citation

Visible laser-induced nucleation and growth of chromium, molybdenum, and tungsten films from the hexacarbonyls: reactivity of carbon monoxide on film surfaces

Houle¹,

Singmaster²

1992

J. Phys. Chem.

View full text Add to dashboard Cite

show abstract

Tandems de composés de tungsténe. Absorbeurs selectifs del'energie solaire Par

Yous¹,

Donnadieu²

1986

phys. stat. sol. (a)

View full text Add to dashboard Cite

Des couches minces de composés de tungsténe ont été préparées sur support de quartz ou silicium, á températures élevées á400 á 480 °C), par d`composition chimique en phase vapeur de l'hexacarbonyle de tungsténe, á pression atmosphérique en présence ou nond'oxygéne. Le tungsténe noir obtenu á 400 °C en présence d'oxygéne présents une bonne absorptivité (a ≈︁ 0,95) mais une trés forte émissivité á 400 °C (e400 °c ° 0,54). Le tungsténe réflecteur préparé a 480 °C, sans apport d'oxygéne, posséde des caractéristiques inverses: mauvaise absorptivité (a ≈︁ 0,49), mais une émissivité a 400 °C correcte (e400 °C ≈︁ 0,11). Nous proposons trois voies pour améliorer la sélectivité spectrale de ces matériaux en vue d'une application en conversion photothermique de l'énergie solaire á moyenne température.

show abstract

Chemically vapour-deposited tungsten compounds for photothermal converter layers

1985

View full text Add to dashboard Cite

Effet de la structure sur les propriétés optiques de couches minces de composés de tungstène obtenues par décomposition en phase vapeur: Influence sur la sélectivité spectrale

Cited by 12 publications

References 9 publications

Visible laser-induced nucleation and growth of chromium, molybdenum, and tungsten films from the hexacarbonyls: reactivity of carbon monoxide on film surfaces

Visible laser-induced nucleation and growth of chromium, molybdenum, and tungsten films from the hexacarbonyls: reactivity of carbon monoxide on film surfaces

Tandems de composés de tungsténe. Absorbeurs selectifs del'energie solaire Par

Chemically vapour-deposited tungsten compounds for photothermal converter layers

Contact Info

Product

Resources

About