Electric field control of Metal- insulator phase transition in VO2 nano-wire channel Tsubasa Sasaki (Tanaka-lab) 2013/5/29

Contents ・ Background Metal-insulator transition(MIT) of strongly-correlated electron(Mott) materials (ex. VO 2 ) How to control of MIT? Mott FET ・ Purpose of my research Control of MIT by electric field ・ Principle of Mott transition ・ My original model ・ Experiment Pulsed laser deposition ( PLD ) Nano imprint lithography ・ Result ・ Summary

Background strongly-correlated electron materials ( 強相関電子系材料 ) VO 2 strongly-correlated electron materials ( 強相関電子系材料 ) VO 2 Mott insulator （モット絶縁 体 ） Temperature Impurity doping Temperature Impurity doping Huge resistivity change (10 3 ～ 10 4 Ω) Huge resistivity change (10 3 ～ 10 4 Ω) Metal-insulator transition(MIT) Temperature change Impurity doping (V 3+,4+,W 6+ ） O 2

Background How to control the MIT? Control of MIT by electric field MIT : metal-insulator transition Porpose of my reserch Mott FET Device Gate DrainSource VGVG Drain current Metal

M.M.Qazilbash et al, Science 318, 1750 (2007) Phase separation with 100 nm-sized domains around Metal-Insulator transition VO 2 Background

Carrier doping by electric field Advantage Doping only carrier （ Not impurity doping ） Flexible(Electric field) Observable(Domain) Using side-gate FET structures Control of MIT by carrier doping Purpose A Source Drain Gate d L W Insulator Metal VO 2 Pt

Principle （ Brinkman Rice ） BR picture Effective mass changes dramatically n 0 =1.69x10 22 cm -3 Effective mass changes greatly band filling is changed ： Features of strongly-correlated electron system Carrier doping not silicon

Mott criterion Principle （ Mott transition ） Insulator Metal Effective Bohr radius P. P. Edwards et al, J. Phys. Chem, 99 (1995) 5228

My original model Carrier doping amount by electric field E g =0.12 eV k B =8.617 ev/K Carrier doping amount by thermal excitation In fact, since the experiment at finite temperature, it is necessary to consider the thermal excitation carrier. Mott criterion(carrier doping)

My original model Insulator Metal Electric field switching Insulator Metal

Experiment(PLD) Pulse laser deposition (PLD) ArF （ λ=193nm ） レーザ 基板 レーザ Al 2 O 3 VO 2 Production of thin film 基板 V 2 O 5 焼結体

Experiment(nanoimprint) Production of structure A optical micrograph Process 4mm 0.5mm

Result A AFM image optical micrograph Successful production of side-gate FET structures VO 2 Pt Nano wire 400nm 300nm

Summary I made an ​​original model using temperature parameter (T) and gate voltage (Vg) combined with the BR picture and the Mott criterion ● I have successfully created side-gate FET structures ● Further work Electronic propaty measurement I will control MIT by electric field