Dense millimeter-tall carpets of vertically aligned carbon nanotubes (VACNTs) were grown using thermal chemical vapor deposition (CVD) from ethylene and hydrogen gases with two or three independently controlled hot zones while introducing controlled flows of oxygen. Through preheating, oxygen and hydrogen reacted through a multi-step reaction to form water, enabling the growth of tall CNT carpets. This process showed a large tolerance for variations of O 2, H 2, and C 2H 4. The measured water vapor produced was half the theoretical maximum. The residence time strongly affected the decomposition of the gases. The simplicity and robustness of this CVD process provides a simpler alternative to direct addition of water vapor for manufacturing tall carpets of aligned CNTs with a high level of control.
Bibliographical noteFunding Information:
This research was supported by the MIT Energy Initiative and by a BSF grant ( USA-Israel Binational Science Foundation ). G.D.N. was partially supported by an Intel Fellowship and by a FP7 Marie Curie Reintegration Grant . Experiments at the University of Michigan were supported by Office of Naval Research Grant # N000141010556 ; the DoD, Air Force Office of Scientific Research, National Defense Science and Engineering Graduate (NDSEG) Fellowship, 32 CFR 168a (to E.S.P.); and a University of Michigan Mechanical Engineering Departmental Fellowship (to C.R.O). We are grateful to Jim Daley and to the staff of the NanoStructures Laboratory (NSL) at MIT for the use of their HRSEM and for the preparation of e-beam evaporated samples. We are grateful to Dr. Ilana Perelshtein for HRTEM, to Dr. Yafit Fleger for HRSEM, and to Dr. Eti Teblum and Efrat Shawat for performing specific synthesis experiments at Bar Ilan.