**4.4 111** f g **tilted facet-surfaces**

**Figure 13(a)** shows a typical filtered RHEED pattern obtained from the 111 f g facet sample at *θ*<sup>g</sup> = +0.7° and *ϕ* = +2.7° after flashing in UHV. The RHEED pattern showed notable characteristics, consisting of tilted 7�7 spots (some are marked by yellow circles, and 1/7th-order Laue zones, L1/7-L6/7, are recognized) and

faint horizontal 16�2 spots (cyan circles). The 7�7 pattern was tilted in the counterclockwise direction around DB, and the tilt angle was �36°, which is

*Creation and Evaluation of Atomically Ordered Side- and Facet-Surface Structures of Three…*

**Figure 13(b)** shows a simulated RHEED pattern from the 111 ð Þ facet-surface, corresponding to Ewald sphere cross sections of 2D 7�7 reciprocal lattice rods of the tilted Si 111 ð Þ. The excellent agreement between **Figure 13(a)** and **(b)** indicates the creation of an atomically ordered Si 111 ð Þ7�7 facet-surface. The fabricated 3D structure shows that the relative glancing and azimuth angles to the tilted Si 111 ð Þ facet-surface are 2.1 and 1.8°, respectively, under this condition. These RHEED patterns clearly show the existence of three different atomically ordered surfaces on the 111 f g facet sample, that is, the 110 ð Þ bottom, 111 ð Þ facet, and 111 � � facet-surfaces. One can see the characteristic *ϕ* dependence of the RHEED patterns in Ref [9].

The creation and observation methods for well-defined surfaces enable the epitaxial growth of an arbitrary geometry, a key technique for nanoconstruction in 3D space [26–31]. Therefore, our established methodology contributes to the realization of well-ordered 3D nanofabrication, where the material stacking direction can be perfectly switched between the out-of-plane and in-plane directions. Novel 3D nanostructures are also expected to help unveil the underlying 3D surface science phenomena. Finally, two demonstrations utilizing a 3D architected Si platform are

Atomically well-defined side-surfaces on a substrate can make an enormous contribution to nanofabrication [26–31]. To demonstrate the applicability of mate-

reconstructed side-surface structures on 3D Si with vertical 111 f g7�7 side-surfaces. Ag and Fe layers with thickness of 1.0 and 0.4 nm were deposited on the 111 � � leftside and 111 � � right-side surfaces, respectively, and the sample was subsequently

**Figure 14(a)** and **(b)** show typical RHEED patterns obtained from the left-side

<sup>3</sup> <sup>p</sup> -Ag [4, 24, 31, 32] was obtained on the left-side surface. These

(orange arrows) in **Figure 14(a)**. In **Figure 14(b)**, we can confirm 2�2 (streaky) spots (orange arrows), showing the formation of c-FeSi [18]. Simultaneously,

results show that highly developed thin-film formation techniques are applicable for the vertical side-surface of 3D patterned substrates and the material stacking direction can be perfectly switched between the out-of-plane and in-plane

**Figure 14(c)** and **(d)** show cross-sectional TEM images of the 0.4-nm-thick Fe layer deposited on the 111 � � right-side surface and the 5.0-nm-thick Ag deposited on the 111 � � left-side surface. We can see four and five MLs of *α*-Fe [18] on the 111 � � right-side surface (**Figure 14(d)**), where a smooth in-plane heteroepitaxial interface with a length of 50 nm or more was formed between *α*-Fe and Si. The orientation relations between the *α*-Fe and the Si right-side surface are 111 � �Fe∥ 111 � �Si and <sup>112</sup> � �Fe<sup>∥</sup> <sup>112</sup> � �Si, similar to those indicated in previous reports on Fe on a 2D Si 111 ð Þ surface [18, 33, 34]. A cross-sectional TEM image for Ag deposited on the 111 � �

<sup>3</sup> <sup>p</sup> � ffiffiffi

<sup>3</sup> <sup>p</sup> (streaky) spots in L0

rial growth on such side-surfaces, we produced Si 111 f g-Fe and Si 111 f g-Ag

consistent with *θ*F.

shown.

Si(111) ffiffiffi 3 <sup>p</sup> � ffiffiffi

directions.

**103**

annealed at 500°C in UHV.

**5. Application of 3D architected Si**

*DOI: http://dx.doi.org/10.5772/intechopen.92860*

**5.1 Platform for material growth on 3D surfaces**

and right-side surfaces, respectively. We can confirm ffiffiffi

*(a) RHEED pattern from the* f g 110 *vertical sample observed at* θ *= +0.4*° *and* ϕ *= +1.1*° *with eye guides of Laue zone. Schematics of 2D reciprocal lattices on (b) Si*ð Þ 100 *2*�*1 and (c) Si*ð Þ 011 *16*�*2, corresponding to the top/bottom and right-side surfaces, respectively, as shown in (d).*

#### **Figure 13.**

*(a) RHEED pattern for the* f g 111 *facet sample at* θ *= +0.7*° *and* ϕ *= +2.7*°*. The pattern consists of a* ð Þ 111 *7*�*7 pattern tilted* �*36*° *in the counterclockwise direction (yellow circles) and a faint 16*�*2 pattern (cyan circles). (b) Simulated RHEED pattern (left) reflecting geometric relationship (bottom right). The upper right figure represents the corresponding 2D reciprocal lattice normal to the facet direction.*

*Creation and Evaluation of Atomically Ordered Side- and Facet-Surface Structures of Three… DOI: http://dx.doi.org/10.5772/intechopen.92860*

faint horizontal 16�2 spots (cyan circles). The 7�7 pattern was tilted in the counterclockwise direction around DB, and the tilt angle was �36°, which is consistent with *θ*F.

**Figure 13(b)** shows a simulated RHEED pattern from the 111 ð Þ facet-surface, corresponding to Ewald sphere cross sections of 2D 7�7 reciprocal lattice rods of the tilted Si 111 ð Þ. The excellent agreement between **Figure 13(a)** and **(b)** indicates the creation of an atomically ordered Si 111 ð Þ7�7 facet-surface. The fabricated 3D structure shows that the relative glancing and azimuth angles to the tilted Si 111 ð Þ facet-surface are 2.1 and 1.8°, respectively, under this condition. These RHEED patterns clearly show the existence of three different atomically ordered surfaces on the 111 f g facet sample, that is, the 110 ð Þ bottom, 111 ð Þ facet, and 111 � � facet-surfaces. One can see the characteristic *ϕ* dependence of the RHEED patterns in Ref [9].
