TY - JOUR

T1 - Growth and characterization of 7,7,8,8-tetracyano-quinodimethane crystals on chemical vapor deposition graphene

AU - Black, Andrés

AU - Jimenez, Fernando

AU - Bernardo Gavito, Ramon

AU - Casado, Santiago

AU - Granados, Daniel

AU - Vázquez De Parga, Amadeo L.

N1 - This is the author’s version of a work that was accepted for publication in Journal of Crystal Growth. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Crystal Growth, 453, 2016 DOI: 10.1016/j.jcrysgro.2016.07.023

PY - 2016/11/1

Y1 - 2016/11/1

N2 - Chemical functionalization of graphene could pave the way for favorably modifying its already remarkable properties. Organic molecules have been utilized to this end as a way to alter graphene’s structural, chemical, electrical, optical and even magnetic properties. One such promising organic molecule is 7,7,8,8-tetracyano-quinodimethane (TCNQ), a strong electron acceptor which has been shown to be an effective p-dopant of graphene. This study explores the thermal evaporation of TCNQ onto graphene transferred onto SiO2/Si substrates. Using two different home-made thermal evaporators, a wide range of TCNQ growth regimes are explored, from thin films to crystals . The resulting graphene/TCNQ structure is characterized via optical microscopy, Raman spectroscopy and atomic force microscopy (AFM). TCNQ films are found to be comprised of TCNQ and the oxidized product of TCNQ, α,α-dicyano-p-toluoylcyanide (DCTC), which confirms the electron charge transfer from graphene to the TCNQ films. AFM measurements of these films show that after forming a rather smooth layer covering the graphene surface, small clusters start to form. For higher TCNQ coverage, the clusters agglomerate, becoming quite large in size and forming ripples or wrinkles across the surface.

AB - Chemical functionalization of graphene could pave the way for favorably modifying its already remarkable properties. Organic molecules have been utilized to this end as a way to alter graphene’s structural, chemical, electrical, optical and even magnetic properties. One such promising organic molecule is 7,7,8,8-tetracyano-quinodimethane (TCNQ), a strong electron acceptor which has been shown to be an effective p-dopant of graphene. This study explores the thermal evaporation of TCNQ onto graphene transferred onto SiO2/Si substrates. Using two different home-made thermal evaporators, a wide range of TCNQ growth regimes are explored, from thin films to crystals . The resulting graphene/TCNQ structure is characterized via optical microscopy, Raman spectroscopy and atomic force microscopy (AFM). TCNQ films are found to be comprised of TCNQ and the oxidized product of TCNQ, α,α-dicyano-p-toluoylcyanide (DCTC), which confirms the electron charge transfer from graphene to the TCNQ films. AFM measurements of these films show that after forming a rather smooth layer covering the graphene surface, small clusters start to form. For higher TCNQ coverage, the clusters agglomerate, becoming quite large in size and forming ripples or wrinkles across the surface.

KW - A1. Diffusion

KW - A1. Nanostructures

KW - A3. Physical vapor deposition processes

KW - B1. Organic compounds

U2 - 10.1016/j.jcrysgro.2016.07.023

DO - 10.1016/j.jcrysgro.2016.07.023

M3 - Journal article

VL - 453

SP - 1

EP - 6

JO - Journal of Crystal Growth

JF - Journal of Crystal Growth

SN - 0022-0248

ER -