12.3.1 Top-Down Approach

The top-down methods are popular and easy as compared to the bottom-up methods.

The most common and famous top-down process used for the fabrication of the materials

is a combination of photolithography and the dry/wet etching method. This method

is used for the synthesis of wide bandgap (WBG) semiconducting micromaterials on a

silicon substrate [20]. In addition, the electron beam lithography (EBL) or focused ion

beam (FIB) is used for the nanofabrication of WBG materials. Figure 12.3 shows lift-off

and negative mask surface nano-machining practices for the production the silicon car­

bide nanowires (NWs) and their applications in the device such as nano-electrochemical

switches [26]. Another method that is similar to conventional photolithography is elec­

tron beam lithography (EBL). The drawing of the pattern with sub-10 nm resolution can

be done with the help of the EBL as a top-down approach. After fabricating, the micro-

nonostructures are transferred to soft platforms using the dry transfer printing process.

12.3.2 Bottom-Up Approach

In the bottom-up approach, various materials have been grown by different techniques. A

few of them are listed in this section. The three-dimensional, meticulous graphene on

silicon nanowire mesh pattern was reported with personalized electron transfer and

absorption properties. These selected properties can be used for future applications

where it is needed like sensor, energy, and bioelectronics. The growth condition during

the synthesis of the graphene-like growth time and pressure of methane gives novel

properties to the material [27]. Sapphire substrate has been used for the synthesis of very

long self-organized GaN nano-wires with hexagonal sections. Here, the GaN was

FIGURE 12.3

(a, b) SiC nanowires (NWs) lift-off and negative mask surface nano-machining processes for making the SiC

NWs, (c) a 20 μm long SiC NW, (d) close-in view of the device, (e) typical nonmetallized SiC NWs and gaps

achieved by the negative mask process in this work. Adapted with permission [ 26]. Copyright 2010. American

Chemical Society.

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Bioelectronics