Conformal Coating by High Pressure Chemical Deposition for Patterned Microwires of II–VI Semiconductors

Abstract

Deposition techniques that can uniformly and conformally coat deep trenches and very high aspect ratio pores with uniform thickness fi lms are valuable in the synthesis of complex three-dimensionally structured materials. Here it is shown that high pressure chemical vapor deposition can be used to deposit conformal fi lms of II-VI semiconductors such as ZnSe, ZnS, and ZnO into high aspect ratio pores. Microstructured optical fi bers serve as tailored templates for the patterning of II-VI semiconductor microwire arrays of these materials with precision and fl exibility. In this way, centimeters-long microwires with exterior surfaces that conform well to the nearly atomically smooth silica templates can be fabricated by conformal coating. This process allows for II-VI semiconductors, which cannot be processed into optical fi bers with conventional techniques, to be fabricated into step index and microstructured optical fi bers.

Infrared fibers

“…Deposition of a Zn-S/Se cladding layer followed by a ZnSe core can allow for complete elimination of the mode overlap with silica present in silica clad ZnSe fibers (Fig. 10) [392]. Appropriate modification of the grain/microstructure may allow for considerably lower optical losses, as the intrinsic optical loss of ZnSe is very low [73].…”

“…(c) InSb core, borosilicate glass cladding fiber. [17,73,392]. High pressures facilitate mass transport into the silica fiber pores [74].…”

“…Although this approach may not produce the fiber lengths typically resulting from thermally drawing a preform, useful active fiber devices may be produced. For example, IR-transparent ZnSe [17], a wide-gap II-VI semiconductor [392] that finds many optical and optoelectronic applications, has been deposited via CVD in the hollow core of a silica fiber while maintaining high-quality polycrystallinity. It is conceivable that such fibers may lead to novel IR fiber lasers at wavelengths extending beyond 2 μm [393].…”

Templated growth of II-VI semiconductor optical fiber devices and steps towards infrared fiber lasers

“…We anticipate that through the use of higher pressures, the interior diameter could be reduced even further or the hole could even be eliminated. As well as simple capillaries, the very high aspect ratio pores in silica microstructured optical fiber (MOF) templates can be deposited with the II-VI materials ZnS and ZnS x Se (1−x) via HPCVD 14 . This coating proceeds such that precisely patterned, centimeters-long arrays of wires micrometers in diameter can be formed.…”

Hybrid Optical Fibers – An Innovative Platform for In‐Fiber Photonic Devices

“…One particularly interesting example is a concentric semiconductor multilayer of differently doped semiconductors in a PCF, which represented an entirely fi ber-integrated semiconductor homojunction (Figure 4 b). [ 65 ] More recent works extend towards integrating other semiconductor materials into microstructured fi bers and capillaries such as II-VI semiconductors (e.g., ZnS or ZnSe) [ 67 ] (Figure 4 …”