Localized Synthesis of Carbon Nanotube Films on Suspended Microstructures by Laser-Assisted Chemical Vapor Deposition

Abstract

A laser-assisted chemical vapor deposition (LCVD) method has been developed for in situ synthesis of carbon nanotube (CNT) films on suspended microstructures. Focused laser beams are used to heat locally the suspended microstructures with low thermal mass and low thermal dissipation to high temperatures for localized CNT growth. Other substrate areas than the microstructures remain at low temperatures, preventing the devices on the substrate from being destroyed by high temperatures. The synthesizing parameters and the influences on CNT morphology and structures are systematically investigated and optimized, and solutions for uniform temperature distribution are proposed. Upon optimization, uniform, localized, and rapid growth of CNT synthesis has been achieved on suspended microstructures, and aligned CNTs with length and uniformity comparable to conventional hot-wall CVD have been successfully obtained. The experimental results show LCVD is a promising technology for in situ and localized synthesis of CNT films on suspended microstructures for CNT-CMOS (complementary metal oxide semiconductor) integration.Index Terms-Carbon nanotube (CNT), complementary metal oxide semiconductor (CMOS), integration, laser, microstructure.

Carbon nanotube catalysts: recent advances in synthesis, characterization and applications

“…With particle size around a few nm, SWNTs are formed and the particles larger than 10 nm favour the formation of MWNTs. 63 Many CVD alternatives have been established, including fixed beds, [64][65][66][67][68] fluidized beds, 7,69-73 aerosols, [74][75][76] floating catalysts, [77][78][79] and combination methods [80][81][82][83][84] such as plasmaenhanced 80,81 and laser-assisted CVD techniques. [82][83][84] The hybrid systems combining CVD, laser ablation and arc discharge are capable of improving the quality and yield in contrast to conventional CVD techniques.…”

“…63 Many CVD alternatives have been established, including fixed beds, [64][65][66][67][68] fluidized beds, 7,69-73 aerosols, [74][75][76] floating catalysts, [77][78][79] and combination methods [80][81][82][83][84] such as plasmaenhanced 80,81 and laser-assisted CVD techniques. [82][83][84] The hybrid systems combining CVD, laser ablation and arc discharge are capable of improving the quality and yield in contrast to conventional CVD techniques. [85][86][87] However, they obfuscate the fundamental scale-up and hence the hybrid reactor systems are confronted with the same scale-up problems which restrict arc discharge and laser ablation methods.…”

“…156 This process may have beneficial applications in fabricating CNT sensors on integrated circuits for improved performance. 83 2.3.4 Plasma-assisted CVD. In recent years, the plasma-assisted CVD approach has caught great attention.…”

Co-catalytic Absorption Layers for Controlled Laser-Induced Chemical Vapor Deposition of Carbon Nanotubes

“…Chemical vapor deposition (CVD), in which CNTs nucleate and grow from catalyst nanoparticles exposed to hydrocarbon precursors at elevated temperatures, has become the dominant growth technique due to its versatility and scalability. To enable CMOS back-end compatibility and direct CNT integration on temperature-sensitive flexible substrates, a range of local heating strategies have been explored, in particular laser-induced CVD (LiCVD). − An opaque absorption layer is widely used for effective local heating in combination with high laser powers. − ,,− More controlled CNT LiCVD requires a detailed understanding of the catalytic growth process and the related laser interactions. Crucial to this, albeit widely neglected in the current literature, are process-specific increases in optical absorption arising from initial reduction of the transition-metal nanoparticle catalysts typically used, such as Fe, and the ever increasing amount of carbon deposited.…”

Direct Synthesis of Carbon Nanotubes in CMOS-Layout of Micro-heaters

“…However, suspended micro-heaters would be susceptible to mechanical deformation, mainly due to stiction and buckling during the dielectric etching and joule heating process. Compared to MEMS, CMOS structures are more vulnerable to the mentioned processes [11]. Therefore, we intend to perform limited dielectric under-etching on the CMOS micro-heaters to achieve required thermal gradient while maintaining necessary mechanical stability [9].…”