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Pure electron-electron dephasing in percolative aluminum ultrathin film grown by molecular beam epitaxy.

Lin SW, Wu YH, Chang L, Liang CT, Lin SD - Nanoscale Res Lett (2015)

Bottom Line: We have successfully grown ultrathin continuous aluminum film by molecular beam epitaxy.This percolative aluminum film is single crystalline and strain free as characterized by transmission electron microscopy and atomic force microscopy.The weak anti-localization effect is observed in the temperature range of 1.4 to 10 K with this sample, and it reveals that, for the first time, the dephasing is purely caused by electron-electron inelastic scattering in aluminum.

View Article: PubMed Central - PubMed

Affiliation: Department of Electronics Engineering, National Chiao Tung University, 1001 University Road, Hsinchu, 30010 Taiwan.

ABSTRACT
We have successfully grown ultrathin continuous aluminum film by molecular beam epitaxy. This percolative aluminum film is single crystalline and strain free as characterized by transmission electron microscopy and atomic force microscopy. The weak anti-localization effect is observed in the temperature range of 1.4 to 10 K with this sample, and it reveals that, for the first time, the dephasing is purely caused by electron-electron inelastic scattering in aluminum.

No MeSH data available.


Related in: MedlinePlus

The 1 × 1 μm2AFM image of the Al sample showing the sample roughness is about 4.9 nm.
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Fig2: The 1 × 1 μm2AFM image of the Al sample showing the sample roughness is about 4.9 nm.

Mentions: We have used cross-sectional high-resolution transmission electron microscopy (TEM) and atomic force microscopy (AFM) for the investigation of film crystal quality and surface morphology. Figure 1 shows the TEM image of our epitaxial Al film taken with electron beam along the zone axis. A clear interface between the GaAs template and deposited Al can be seen in the middle of the picture. At the bottom of Figure 1, we can see an amorphous layer which may be amorphous carbon from TEM specimen preparation. The thickness of Al layer is about 8 nm which is thicker than the deposited amount because our Al film is percolative as we shall see later in the AFM images. A detailed examination of the TEM image at the interface can show the existence of misfit dislocations, implying that most of the strain in the Al film caused by lattice mismatch between Al and GaAs is released. The inset of Figure 1 is the fast Fourier transform diffraction pattern taken around the interface between GaAs and Al. Clear diffraction spots can be seen. The inner hexagon is the diffraction spots of the bottom GaAs template, and the outer one is for epi-aluminum film, indicating that the epitaxial relationship of Al with GaAs is (100)GaAs // (111)Al, <011 > GaAs // , and // ; the last axis is also the observation plane of the TEM image. The axis arrangement is different from the previous works [20-22] probably due to the different surface conditions used. Clear spots indicating good crystal quality and no deformation of the diffraction spots are observed even the strain accumulation due to lattice mismatch could occur in our sample. Figure 2 shows a 1 × 1 μm2 AFM image of our Al film. Obviously, a percolating but continuous morphology has been seen. This kind of morphology was generally observed when metal films are deposited onto a semiconductor or dielectric template because of poor affinity between them [23]. Although the bi-polarized atomic bonding of the bottom GaAs template or inhomogeneous surface atomic deformation could also play a role here, we have used a smooth Ga-rich surface as the epitaxial template to minimize these two issues. The roughness of the film is about 4.9 nm which is thicker than the deposited thickness and is possibly caused by the Al oxidation after the exposure to the air.Figure 1


Pure electron-electron dephasing in percolative aluminum ultrathin film grown by molecular beam epitaxy.

Lin SW, Wu YH, Chang L, Liang CT, Lin SD - Nanoscale Res Lett (2015)

The 1 × 1 μm2AFM image of the Al sample showing the sample roughness is about 4.9 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385055&req=5

Fig2: The 1 × 1 μm2AFM image of the Al sample showing the sample roughness is about 4.9 nm.
Mentions: We have used cross-sectional high-resolution transmission electron microscopy (TEM) and atomic force microscopy (AFM) for the investigation of film crystal quality and surface morphology. Figure 1 shows the TEM image of our epitaxial Al film taken with electron beam along the zone axis. A clear interface between the GaAs template and deposited Al can be seen in the middle of the picture. At the bottom of Figure 1, we can see an amorphous layer which may be amorphous carbon from TEM specimen preparation. The thickness of Al layer is about 8 nm which is thicker than the deposited amount because our Al film is percolative as we shall see later in the AFM images. A detailed examination of the TEM image at the interface can show the existence of misfit dislocations, implying that most of the strain in the Al film caused by lattice mismatch between Al and GaAs is released. The inset of Figure 1 is the fast Fourier transform diffraction pattern taken around the interface between GaAs and Al. Clear diffraction spots can be seen. The inner hexagon is the diffraction spots of the bottom GaAs template, and the outer one is for epi-aluminum film, indicating that the epitaxial relationship of Al with GaAs is (100)GaAs // (111)Al, <011 > GaAs // , and // ; the last axis is also the observation plane of the TEM image. The axis arrangement is different from the previous works [20-22] probably due to the different surface conditions used. Clear spots indicating good crystal quality and no deformation of the diffraction spots are observed even the strain accumulation due to lattice mismatch could occur in our sample. Figure 2 shows a 1 × 1 μm2 AFM image of our Al film. Obviously, a percolating but continuous morphology has been seen. This kind of morphology was generally observed when metal films are deposited onto a semiconductor or dielectric template because of poor affinity between them [23]. Although the bi-polarized atomic bonding of the bottom GaAs template or inhomogeneous surface atomic deformation could also play a role here, we have used a smooth Ga-rich surface as the epitaxial template to minimize these two issues. The roughness of the film is about 4.9 nm which is thicker than the deposited thickness and is possibly caused by the Al oxidation after the exposure to the air.Figure 1

Bottom Line: We have successfully grown ultrathin continuous aluminum film by molecular beam epitaxy.This percolative aluminum film is single crystalline and strain free as characterized by transmission electron microscopy and atomic force microscopy.The weak anti-localization effect is observed in the temperature range of 1.4 to 10 K with this sample, and it reveals that, for the first time, the dephasing is purely caused by electron-electron inelastic scattering in aluminum.

View Article: PubMed Central - PubMed

Affiliation: Department of Electronics Engineering, National Chiao Tung University, 1001 University Road, Hsinchu, 30010 Taiwan.

ABSTRACT
We have successfully grown ultrathin continuous aluminum film by molecular beam epitaxy. This percolative aluminum film is single crystalline and strain free as characterized by transmission electron microscopy and atomic force microscopy. The weak anti-localization effect is observed in the temperature range of 1.4 to 10 K with this sample, and it reveals that, for the first time, the dephasing is purely caused by electron-electron inelastic scattering in aluminum.

No MeSH data available.


Related in: MedlinePlus