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Investigations of ripple pattern formation on Germanium surfaces using 100-keV Ar(+) ions.

Sulania I, Agarwal D, Husain M, Avasthi DK - Nanoscale Res Lett (2015)

Bottom Line: The formation of nanoripples initiates at an angle of θ ~ 45°.Ripple pattern formation has taken place on the Ge surface in the energy regime of 100 keV as compared to the other reports which had been carried out using very low energy ions.Raman spectra reveal that the near surface of crystalline Ge samples becomes amorphous due to interaction of Ar(+) ions due to creation of defects through collision cascades.

View Article: PubMed Central - PubMed

Affiliation: Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi, 110067 India ; Jamia Millia Islamia, Jamia Nagar, New Delhi, 110025 India.

ABSTRACT
We have investigated the formation of nanoripples on the surface of germanium, Ge(100), due to the effect of 100-keV Ar (+) ion irradiation. The irradiation was carried out at different incidence angles from 0° to 75° in steps of 15° with respect to the surface normal with a fixed ion fluence of approximately 3 × 10(17) ions/cm(2). Atomic force micrographs show an increase in surface roughness from 0.5 to 4.3 nm for the pristine sample and the sample irradiated at 60° incidence angle due to cos(-1)(θ) dependence on sputtering yield. With increase in angle of incidence, there is transition observed from nanodots to aligned nanodots perpendicular to the direction of the beam. There is an increase in size of the nanostructures observed from 44 to 103 nm with angle of incidence. The formation of nanoripples initiates at an angle of θ ~ 45°. Ripple pattern formation has taken place on the Ge surface in the energy regime of 100 keV as compared to the other reports which had been carried out using very low energy ions. Raman spectra reveal that the near surface of crystalline Ge samples becomes amorphous due to interaction of Ar(+) ions due to creation of defects through collision cascades.

No MeSH data available.


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AFM micrographs of the irradiated at fluence 3 × 1017ions/cm2sample of Ge(100). At angles of incidence of (a) 0°, (b) 15°, (c) 30°, (d) 45°, (e) 60°, and (f) 75° (all images in 2 × 2 μm2 scan size).
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Fig2: AFM micrographs of the irradiated at fluence 3 × 1017ions/cm2sample of Ge(100). At angles of incidence of (a) 0°, (b) 15°, (c) 30°, (d) 45°, (e) 60°, and (f) 75° (all images in 2 × 2 μm2 scan size).

Mentions: The AFM micrograph of the pristine Ge(100) sample is shown in Figure 1. The surface of the pristine sample is smooth with a rms roughness of 0.2 nm. Figure 2 shows the surface morphology of the samples irradiated at different angles of incidence with respect to the surface normal using 100-keV Ar+ ions with a fluence of approximately 3 × 1017 ions/cm2. It is clear from the AFM micrographs that when the sample was irradiated at 0°, the dot structures started to evolve on the surface of Ge(100) with initial increases in rms roughness to 0.5 nm as compared to 0.2 nm of the pristine sample. The average size of the nanodots was found to be approximately 44 nm as determined by the line profile of the AFM image (Figure 3). At 15° incidence, the dot size increases to 55 nm and the roughness to 0.97 nm. On further increasing the angle to 30°, the alignment of the dots was observed perpendicular to the direction of the beam (shown with the arrow). The rms roughness increases to 3.4 nm, and the size of the dots increases to 93 nm. The wavelength of the aligned pattern was observed to be 120 nm. At 45°, the alignment becomes prominently visible perpendicular to the beam direction. This is the transition angle for ripple pattern to form on Ge. The rms roughness increased to 3.7 nm. The size of the dots was observed to be 95 nm and wavelength of the aligned nanodots as 128 nm. On further increasing the angle to 60°, the roughness of the samples increases to 4.3 nm. The alignment was more prominent and the formation of ripples at this angle is well observed, although the ripples are not continuous in nature. The wavelength of the ripples was found to be 140 nm and size of the dots observed to be 103 nm (Figure 3). Bradley et al. have shown that for the single element material, the formation of continuous or ordered ripples is less probable as compared to the one with binary material [31]. For the case of InP bombarded with 1.5-keV Ar ions, we have observed the formation of ripple pattern at 63° angle of incidence [4]. Moreover, the ripples were found growing continuous on the surface of the sample unlike those seen as chains of dots on Ge in the present case. The direction of the ripple formation was along the beam direction in InP [4] unlike Ge where the direction of ripples is perpendicular to the direction of the beam (shown by the arrow in Figure 2). Due to the single element, the surface sputtering takes place uniformly on the material, thus giving rise to chains of dots pattern. At an incidence angle of 75°, it was observed that the surface looks similar to that of the pristine sample, with slight increase in the roughness value of 0.3 nm as compared to 0.2 nm of the pristine sample. At this angle, the reflection of ions takes place which decreases the probability of interaction of the ions with the sample surface and does not change much in comparison to the pristine sample.Figure 1


Investigations of ripple pattern formation on Germanium surfaces using 100-keV Ar(+) ions.

Sulania I, Agarwal D, Husain M, Avasthi DK - Nanoscale Res Lett (2015)

AFM micrographs of the irradiated at fluence 3 × 1017ions/cm2sample of Ge(100). At angles of incidence of (a) 0°, (b) 15°, (c) 30°, (d) 45°, (e) 60°, and (f) 75° (all images in 2 × 2 μm2 scan size).
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Fig2: AFM micrographs of the irradiated at fluence 3 × 1017ions/cm2sample of Ge(100). At angles of incidence of (a) 0°, (b) 15°, (c) 30°, (d) 45°, (e) 60°, and (f) 75° (all images in 2 × 2 μm2 scan size).
Mentions: The AFM micrograph of the pristine Ge(100) sample is shown in Figure 1. The surface of the pristine sample is smooth with a rms roughness of 0.2 nm. Figure 2 shows the surface morphology of the samples irradiated at different angles of incidence with respect to the surface normal using 100-keV Ar+ ions with a fluence of approximately 3 × 1017 ions/cm2. It is clear from the AFM micrographs that when the sample was irradiated at 0°, the dot structures started to evolve on the surface of Ge(100) with initial increases in rms roughness to 0.5 nm as compared to 0.2 nm of the pristine sample. The average size of the nanodots was found to be approximately 44 nm as determined by the line profile of the AFM image (Figure 3). At 15° incidence, the dot size increases to 55 nm and the roughness to 0.97 nm. On further increasing the angle to 30°, the alignment of the dots was observed perpendicular to the direction of the beam (shown with the arrow). The rms roughness increases to 3.4 nm, and the size of the dots increases to 93 nm. The wavelength of the aligned pattern was observed to be 120 nm. At 45°, the alignment becomes prominently visible perpendicular to the beam direction. This is the transition angle for ripple pattern to form on Ge. The rms roughness increased to 3.7 nm. The size of the dots was observed to be 95 nm and wavelength of the aligned nanodots as 128 nm. On further increasing the angle to 60°, the roughness of the samples increases to 4.3 nm. The alignment was more prominent and the formation of ripples at this angle is well observed, although the ripples are not continuous in nature. The wavelength of the ripples was found to be 140 nm and size of the dots observed to be 103 nm (Figure 3). Bradley et al. have shown that for the single element material, the formation of continuous or ordered ripples is less probable as compared to the one with binary material [31]. For the case of InP bombarded with 1.5-keV Ar ions, we have observed the formation of ripple pattern at 63° angle of incidence [4]. Moreover, the ripples were found growing continuous on the surface of the sample unlike those seen as chains of dots on Ge in the present case. The direction of the ripple formation was along the beam direction in InP [4] unlike Ge where the direction of ripples is perpendicular to the direction of the beam (shown by the arrow in Figure 2). Due to the single element, the surface sputtering takes place uniformly on the material, thus giving rise to chains of dots pattern. At an incidence angle of 75°, it was observed that the surface looks similar to that of the pristine sample, with slight increase in the roughness value of 0.3 nm as compared to 0.2 nm of the pristine sample. At this angle, the reflection of ions takes place which decreases the probability of interaction of the ions with the sample surface and does not change much in comparison to the pristine sample.Figure 1

Bottom Line: The formation of nanoripples initiates at an angle of θ ~ 45°.Ripple pattern formation has taken place on the Ge surface in the energy regime of 100 keV as compared to the other reports which had been carried out using very low energy ions.Raman spectra reveal that the near surface of crystalline Ge samples becomes amorphous due to interaction of Ar(+) ions due to creation of defects through collision cascades.

View Article: PubMed Central - PubMed

Affiliation: Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi, 110067 India ; Jamia Millia Islamia, Jamia Nagar, New Delhi, 110025 India.

ABSTRACT
We have investigated the formation of nanoripples on the surface of germanium, Ge(100), due to the effect of 100-keV Ar (+) ion irradiation. The irradiation was carried out at different incidence angles from 0° to 75° in steps of 15° with respect to the surface normal with a fixed ion fluence of approximately 3 × 10(17) ions/cm(2). Atomic force micrographs show an increase in surface roughness from 0.5 to 4.3 nm for the pristine sample and the sample irradiated at 60° incidence angle due to cos(-1)(θ) dependence on sputtering yield. With increase in angle of incidence, there is transition observed from nanodots to aligned nanodots perpendicular to the direction of the beam. There is an increase in size of the nanostructures observed from 44 to 103 nm with angle of incidence. The formation of nanoripples initiates at an angle of θ ~ 45°. Ripple pattern formation has taken place on the Ge surface in the energy regime of 100 keV as compared to the other reports which had been carried out using very low energy ions. Raman spectra reveal that the near surface of crystalline Ge samples becomes amorphous due to interaction of Ar(+) ions due to creation of defects through collision cascades.

No MeSH data available.


Related in: MedlinePlus