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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.


Optical characterizations of fabricated freestanding HfO2 gratings. (a) optical micrograph of freestanding HfO2 gratings; (b) the reflectance spectra of freestanding HfO2 gratings in the telecommunication range.
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Figure 4: Optical characterizations of fabricated freestanding HfO2 gratings. (a) optical micrograph of freestanding HfO2 gratings; (b) the reflectance spectra of freestanding HfO2 gratings in the telecommunication range.

Mentions: It should be noted that the HfO2 gratings are designed by using rigorous coupled wave analysis (RCWA) method with a commercial code. The generated HfO2 gratings deviate much from the ideal elements used for RCWA simulations (not shown here). The trapezoidal grating profiles, roughness of the grating sidewalls, and variations in silicon surface beneath the grating region degrade the optical performance and result in the spectral shift. Moreover, the available spectral range is from 1460 nm to 1580 nm in our measurement system. Hence, a variety of HfO2 gratings with different grating parameters are fabricated for optical characterization. Figure 4(a) illustrates one optical micrograph of fabricated HfO2 gratings, where the upper two gratings are with the grating widths Wt of 440 nm. The color varies as the grating width changes. The grating widths Wt are about 500 nm for the bottom gratings, and the grating periods are 1020 nm and 1040 nm, respectively. The inset is the magnified view of fabricated HfO2 grating, where the grating period P is 1020 nm and the grating width Wt is about 440 nm. A tunable laser (Agilent 81682A) is used as the light source to characterize the optical response of the fabricated freestanding HfO2 gratings in the telecommunication range. The polarized light beam is incident onto the HfO2 gratings by an infrared objective lens with a numerical aperture of 0.25, and an infrared CCD camera is installed on the setup to acquire sample images. The reflected light is collected and sent to an infrared spectrometer. The experimental spectra are normalized to those of a commercial gold mirror. Figure 4(b) illustrates the reflectance spectra of freestanding HfO2 gratings, where the grating widths Wt are about 440 nm. Taken 1040 nm period HfO2 grating as an example, a broad reflection band that is determined by the refractive index contrast is observed under transverse electric (TE) polarization (TE is polarized in the plane of the grating and parallel to the grating lines) [19]. Two sharp reflection dips are found at 1486 nm and 1562.7 nm with measured reflectance of 10.7% and 4.6%, respectively. Measured reflectances are over 70% in the range of 1499.2 m~1539.5 nm. Since fabricated HfO2 gratings are configured with one-dimensional symmetry, their optical responses are polarization dependent, which are measured by rotating the sample with an angle of 90° with respect to initial measurement. The reflection band shifts and the shape changes under transverse magnetic (TM) polarization (TM is polarized in the plane of the grating and perpendicular to the grating lines). The linear grating reflector is useful for controlling the polarization on a vertical cavity surface emitting device. A blue-shift is observed in reflectance spectra with decreasing the grating period. As the grating period decreases from 1040 nm to 1020 nm, the broad reflection band shifts to shorter wavelength. These results indicate that freestanding HfO2 grating is a promising candidate for single layer dielectric reflector.


Freestanding HfO2 grating fabricated by fast atom beam etching.

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

Optical characterizations of fabricated freestanding HfO2 gratings. (a) optical micrograph of freestanding HfO2 gratings; (b) the reflectance spectra of freestanding HfO2 gratings in the telecommunication range.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC3211457&req=5

Figure 4: Optical characterizations of fabricated freestanding HfO2 gratings. (a) optical micrograph of freestanding HfO2 gratings; (b) the reflectance spectra of freestanding HfO2 gratings in the telecommunication range.
Mentions: It should be noted that the HfO2 gratings are designed by using rigorous coupled wave analysis (RCWA) method with a commercial code. The generated HfO2 gratings deviate much from the ideal elements used for RCWA simulations (not shown here). The trapezoidal grating profiles, roughness of the grating sidewalls, and variations in silicon surface beneath the grating region degrade the optical performance and result in the spectral shift. Moreover, the available spectral range is from 1460 nm to 1580 nm in our measurement system. Hence, a variety of HfO2 gratings with different grating parameters are fabricated for optical characterization. Figure 4(a) illustrates one optical micrograph of fabricated HfO2 gratings, where the upper two gratings are with the grating widths Wt of 440 nm. The color varies as the grating width changes. The grating widths Wt are about 500 nm for the bottom gratings, and the grating periods are 1020 nm and 1040 nm, respectively. The inset is the magnified view of fabricated HfO2 grating, where the grating period P is 1020 nm and the grating width Wt is about 440 nm. A tunable laser (Agilent 81682A) is used as the light source to characterize the optical response of the fabricated freestanding HfO2 gratings in the telecommunication range. The polarized light beam is incident onto the HfO2 gratings by an infrared objective lens with a numerical aperture of 0.25, and an infrared CCD camera is installed on the setup to acquire sample images. The reflected light is collected and sent to an infrared spectrometer. The experimental spectra are normalized to those of a commercial gold mirror. Figure 4(b) illustrates the reflectance spectra of freestanding HfO2 gratings, where the grating widths Wt are about 440 nm. Taken 1040 nm period HfO2 grating as an example, a broad reflection band that is determined by the refractive index contrast is observed under transverse electric (TE) polarization (TE is polarized in the plane of the grating and parallel to the grating lines) [19]. Two sharp reflection dips are found at 1486 nm and 1562.7 nm with measured reflectance of 10.7% and 4.6%, respectively. Measured reflectances are over 70% in the range of 1499.2 m~1539.5 nm. Since fabricated HfO2 gratings are configured with one-dimensional symmetry, their optical responses are polarization dependent, which are measured by rotating the sample with an angle of 90° with respect to initial measurement. The reflection band shifts and the shape changes under transverse magnetic (TM) polarization (TM is polarized in the plane of the grating and perpendicular to the grating lines). The linear grating reflector is useful for controlling the polarization on a vertical cavity surface emitting device. A blue-shift is observed in reflectance spectra with decreasing the grating period. As the grating period decreases from 1040 nm to 1020 nm, the broad reflection band shifts to shorter wavelength. These results indicate that freestanding HfO2 grating is a promising candidate for single layer dielectric reflector.

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.