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Freestanding HfO2 grating fabricated by fast atom beam etching.

Wang Y, Wu T, Kanamori Y, Hane K - Nanoscale Res Lett (2011)

Bottom Line: The silicon substrate beneath the HfO2 grating region is removed to make the HfO2 grating suspend in space.Period- and polarization-dependent optical responses of fabricated HfO2 gratings are experimentally characterized in the reflectance measurements.The simple process is feasible for fabricating freestanding HfO2 grating that is a potential candidate for single layer dielectric reflector.PACS: 73.40.Ty; 42.70.Qs; 81.65.Cf.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Communication Technology, Nanjing University of Posts and Telecommunications, Nanjing, Jiang-Su 210003, People's Republic of China. wyjjy@yahoo.com.

ABSTRACT
We report here the fabrication of freestanding HfO2 grating by combining fast atom beam etching (FAB) of HfO2 film with dry etching of silicon substrate. HfO2 film is deposited onto silicon substrate by electron beam evaporator. The grating patterns are then defined by electron beam lithography and transferred to HfO2 film by FAB etching. The silicon substrate beneath the HfO2 grating region is removed to make the HfO2 grating suspend in space. Period- and polarization-dependent optical responses of fabricated HfO2 gratings are experimentally characterized in the reflectance measurements. The simple process is feasible for fabricating freestanding HfO2 grating that is a potential candidate for single layer dielectric reflector.PACS: 73.40.Ty; 42.70.Qs; 81.65.Cf.

No MeSH data available.


SEM images of fabricated freestanding HfO2 nanostructures. (a) SEM image of a freestanding circular HfO2 grating, the inset is the zoom-in SEM image of circular grating with the grating period of 500 nm; (b) a freestanding HfO2 photonic crystal slab on a GaN-on-silicon platform, the inset is the zoom-in SEM image of HfO2 photonic crystals with the grating period of 600 nm.
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Figure 3: SEM images of fabricated freestanding HfO2 nanostructures. (a) SEM image of a freestanding circular HfO2 grating, the inset is the zoom-in SEM image of circular grating with the grating period of 500 nm; (b) a freestanding HfO2 photonic crystal slab on a GaN-on-silicon platform, the inset is the zoom-in SEM image of HfO2 photonic crystals with the grating period of 600 nm.

Mentions: The simple process is scalable for fabricating suspended HfO2 nanostructures, and facilitates monolithic integration of optoelectronic devices on various material systems. Figure 3(a) shows freestanding circular HfO2 grating, and the inset is the zoom-in SEM image of circular grating with the grating period of 500 nm, where cross arms are connected to the freestanding circular gratings. From the fabrication point of view, the undercut of silicon beneath the HfO2 grating region tends to be difficult when the duty ratio D increases. On the other hand, the long HfO2 grating beams are in the tendency of being fragile, and the deflection and fracture of HfO2 grating beams take place when the duty ratio D decreases. According to our experimental results, the duty ratio D is feasible in the range of 0.3~0.7 to successfully achieve freestanding HfO2 gratings. Moreover, anisotropic and isotropic dry etching of silicon will result in rough silicon surface and large variation in airgap between HfO2 grating and silicon beneath HfO2 grating region, which will degrade the optical performance. In association of deposition and etching techniques, this fabrication issue can be solved and such freestanding HfO2 nanostructures are possible to be incorporated into other material system for serving as the top mirror. Freestanding HfO2 photonic crystals illustrated in Figure 3(b) are realized on a GaN-on-silicon platform, and the inset is the zoom-in SEM image of freestanding photonic crystal structures with the period of 600 nm. Between HfO2 film and GaN layer, one sacrificial film is inserted. After removing the sacrificial layer, HfO2 photonic crystals are freely suspended and the airgap is controlled by the sacrificial layer thickness. These results indicate that the proposed process is feasible to fabricate freestanding HfO2 nanostructures.


Freestanding HfO2 grating fabricated by fast atom beam etching.

Wang Y, Wu T, Kanamori Y, Hane K - Nanoscale Res Lett (2011)

SEM images of fabricated freestanding HfO2 nanostructures. (a) SEM image of a freestanding circular HfO2 grating, the inset is the zoom-in SEM image of circular grating with the grating period of 500 nm; (b) a freestanding HfO2 photonic crystal slab on a GaN-on-silicon platform, the inset is the zoom-in SEM image of HfO2 photonic crystals with the grating period of 600 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211457&req=5

Figure 3: SEM images of fabricated freestanding HfO2 nanostructures. (a) SEM image of a freestanding circular HfO2 grating, the inset is the zoom-in SEM image of circular grating with the grating period of 500 nm; (b) a freestanding HfO2 photonic crystal slab on a GaN-on-silicon platform, the inset is the zoom-in SEM image of HfO2 photonic crystals with the grating period of 600 nm.
Mentions: The simple process is scalable for fabricating suspended HfO2 nanostructures, and facilitates monolithic integration of optoelectronic devices on various material systems. Figure 3(a) shows freestanding circular HfO2 grating, and the inset is the zoom-in SEM image of circular grating with the grating period of 500 nm, where cross arms are connected to the freestanding circular gratings. From the fabrication point of view, the undercut of silicon beneath the HfO2 grating region tends to be difficult when the duty ratio D increases. On the other hand, the long HfO2 grating beams are in the tendency of being fragile, and the deflection and fracture of HfO2 grating beams take place when the duty ratio D decreases. According to our experimental results, the duty ratio D is feasible in the range of 0.3~0.7 to successfully achieve freestanding HfO2 gratings. Moreover, anisotropic and isotropic dry etching of silicon will result in rough silicon surface and large variation in airgap between HfO2 grating and silicon beneath HfO2 grating region, which will degrade the optical performance. In association of deposition and etching techniques, this fabrication issue can be solved and such freestanding HfO2 nanostructures are possible to be incorporated into other material system for serving as the top mirror. Freestanding HfO2 photonic crystals illustrated in Figure 3(b) are realized on a GaN-on-silicon platform, and the inset is the zoom-in SEM image of freestanding photonic crystal structures with the period of 600 nm. Between HfO2 film and GaN layer, one sacrificial film is inserted. After removing the sacrificial layer, HfO2 photonic crystals are freely suspended and the airgap is controlled by the sacrificial layer thickness. These results indicate that the proposed process is feasible to fabricate freestanding HfO2 nanostructures.

Bottom Line: The silicon substrate beneath the HfO2 grating region is removed to make the HfO2 grating suspend in space.Period- and polarization-dependent optical responses of fabricated HfO2 gratings are experimentally characterized in the reflectance measurements.The simple process is feasible for fabricating freestanding HfO2 grating that is a potential candidate for single layer dielectric reflector.PACS: 73.40.Ty; 42.70.Qs; 81.65.Cf.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Communication Technology, Nanjing University of Posts and Telecommunications, Nanjing, Jiang-Su 210003, People's Republic of China. wyjjy@yahoo.com.

ABSTRACT
We report here the fabrication of freestanding HfO2 grating by combining fast atom beam etching (FAB) of HfO2 film with dry etching of silicon substrate. HfO2 film is deposited onto silicon substrate by electron beam evaporator. The grating patterns are then defined by electron beam lithography and transferred to HfO2 film by FAB etching. The silicon substrate beneath the HfO2 grating region is removed to make the HfO2 grating suspend in space. Period- and polarization-dependent optical responses of fabricated HfO2 gratings are experimentally characterized in the reflectance measurements. The simple process is feasible for fabricating freestanding HfO2 grating that is a potential candidate for single layer dielectric reflector.PACS: 73.40.Ty; 42.70.Qs; 81.65.Cf.

No MeSH data available.