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Graphene transfer with self-doping by amorphous thermoplastic resins
Shin, Somyeong,Kim, Seonyeong,Kim, Taekwang,Du, Hyewon,Kim, Ki Soo,Cho, Seungmin,Seo, Sunae Elsevier 2017 Carbon Vol.111 No.-
<P>The wet transfer of graphene requires sacrificial layer, which can support graphene during the removal of metallic substrate and prevent mechanical damage of thin graphene. However, the used polymer layer leaves an amounts of debris or residue on the graphene surface. The typical amorphous thermoplastic resins that consist of macromolecular chains with no crosslinks between the chains have been investigated as sacrificial layers for transferring graphene grown on metallic substrate. We have observed that the strong interaction of graphene and polymer provides clean surface without a chuck of residues and largely diminishes wrinkles and folds of transferred graphene. In addition, due to the increased substrate coupling as well as uniform plausible covalent bonding, we have achieved significant amount of electron transfer from graphene. Thus, polymer-self-doped-graphene during the transfer process has no need for the additional doping process or annealing process in order to obtain clean and flat surface with reduced sheet resistance. No thermal budget makes graphene available towards flexible transparent device application. (C) 2016 Elsevier Ltd. All rights reserved.</P>
Hydrazine Doped Graphene and Its Stability
송민호,서순애,신소명,Taekwang Kim,Hyewon Du,Nayoung Kim,Eunkyu Lee,조승민 한국진공학회 2014 Applied Science and Convergence Technology Vol.23 No.4
The electronic property of graphene was investigated by hydrazine treatment. Hydrazine (N2H4) highly increases electron concentrations and up-shifts Fermi level of graphene based on significant shift of Dirac point to the negative gate voltage. We have observed contact resistance and channel length dependent mobility of graphene in the back-gated device after hydrazine monohydrate treatment and continuously monitored electrical characteristics under Nitrogen or air exposure. The contact resistance increases with hydrazine-treated and subsequent Nitrogen-exposed devices and reduces down in successive Air-exposed device to the similar level of pristine one. The channel conductance curve as a function of gate voltage in hole conduction regime keeps analogous value and shape even after Nitrogen/Air exposure specially whereas, in electron conduction regime change rate of conductance along with the level of conductance with gate voltage are decreased. Hydrazine could be utielized as the highly effective donor without degradation of mobility but the stability issue to be solved for future application.
Kim, Seonyeong,Shin, Somyeong,Kim, Taekwang,Du, Hyewon,Song, Minho,Kim, Ki Soo,Cho, Seungmin,Lee, Sang Wook,Seo, Sunae IOP 2017 Nanotechnology Vol.28 No.17
<P>The modulation of charge carrier concentration allows us to tune the Fermi level (<I>E</I> <SUB>F</SUB>) of graphene thanks to the low electronic density of states near the <I>E</I> <SUB>F</SUB>. The introduced metal oxide thin films as well as the modified transfer process can elaborately maneuver the amounts of charge carrier concentration in graphene. The self-encapsulation provides a solution to overcome the stability issues of metal oxide hole dopants. We have manipulated systematic graphene p-n junction structures for electronic or photonic application-compatible doping methods with current semiconducting process technology. We have demonstrated the anticipated transport properties on the designed heterojunction devices with non-destructive doping methods. This mitigates the device architecture limitation imposed in previously known doping methods. Furthermore, we employed <I>E</I> <SUB>F</SUB>-modulated graphene source/drain (S/D) electrodes in a low dimensional transition metal dichalcogenide field effect transistor (TMDFET). We have succeeded in fulfilling n-type, ambipolar, or p-type field effect transistors (FETs) by moving around only the graphene work function. Besides, the graphene/transition metal dichalcogenide (TMD) junction in either both p- and n-type transistor reveals linear voltage dependence with the enhanced contact resistance. We accomplished the complete conversion of p-/n-channel transistors with S/D tunable electrodes. The <I>E</I> <SUB>F</SUB> modulation using metal oxide facilitates graphene to access state-of-the-art complimentary-metal-oxide-semiconductor (CMOS) technology.</P>
Hydrazine Doped Graphene and Its Stability
Song, MinHo,Shin, Somyeong,Kim, Taekwang,Du, Hyewon,Koo, Hyungjun,Kim, Nayoung,Lee, Eunkyu,Cho, Seungmin,Seo, Sunae The Korean Vacuum Society 2014 Applied Science and Convergence Technology Vol.23 No.4
The electronic property of graphene was investigated by hydrazine treatment. Hydrazine ($N_2H_4$) highly increases electron concentrations and up-shifts Fermi level of graphene based on significant shift of Dirac point to the negative gate voltage. We have observed contact resistance and channel length dependent mobility of graphene in the back-gated device after hydrazine monohydrate treatment and continuously monitored electrical characteristics under Nitrogen or air exposure. The contact resistance increases with hydrazine-treated and subsequent Nitrogen-exposed devices and reduces down in successive Air-exposed device to the similar level of pristine one. The channel conductance curve as a function of gate voltage in hole conduction regime keeps analogous value and shape even after Nitrogen/Air exposure specially whereas, in electron conduction regime change rate of conductance along with the level of conductance with gate voltage are decreased. Hydrazine could be utilized as the highly effective donor without degradation of mobility but the stability issue to be solved for future application.