Diamond:H/Transition Metal Oxides Transfer-Doping: Efficiency and Transistor Performance Dr. Moshe Tordjman Prof. Jesus A. del Alamo Dr. Alon Vardi Dr. Zongyou Yin Prof. Rafi Kalish Dr. Youngtack Lee
Diamond Surface Transfer Doping with Adsorbates Molecules Drawbacks: Before After 1. Volatile and Sensitive to Atmospheric Electron Transfer Equilibrium State Fluctuations. 2. No Temperature Stability. Energy 3. Low Work Function Limited conductivity Energy NEA : CB ‐1.3 eV Vacuum Chemical CB Level Potential µ 2 DHG f E E f f φ~ 4.2eV e‐ Chemical ‐4.2 eV VB VB Potential µ f Adsorbate Adsorbate Acceptor Diamond:H Acceptor Diamond:H X [Å] X [Å] Normal to Surface Normal to Surface Strobel et.al Nature,430, (2004) ; W. Chen, Prog. Surf. Sci (2009)
Diamond Surface Transfer Doping with T ransition M etal O xides Before After Advantages: Electron Transfer Equilibrium State 1. Temperature Stability (up to 350-450 C). 2. Higher Work function Higher conductivity. Energy Energy TMO s Surface Acceptors: NEA : ‐1.3 eV CB Vacuum CBM Level 2 DHG CB E E f f φ> 6.7eV E f VB ‐4.2 eV e‐ VB VBM TMO CB E f Surface VB Acceptor TMO Diamond:H Surface Acceptor Diamond:H X [Å] X [Å] Normal to Surface Normal to Surface Tordjman et. al. Advanced Materials Interfaces , 20130 0155, (2014).
Diamond:H/TMO Transfer Doping Diamond (100) Simplified Structure Measurement Acids Cleaning Diamond:H Hydrogen Plasma TMO Diamond:H In Situ Anneal 350˚C + MoO Thermal Evaporation 3 TMO Diamond:H TMOs come into Various: 1. Crystallization Structures. Van‐Der‐Paw Contacts Hall effect meas. 2. Oxidation phases. (i.e. MoO 3-x , V 2 O 5-x , WO 3-x etc..) 3. Coverage Uniformity. Tordjman et.al. Appl. Phys. Lett.111, 111601 (2017)
MoO 3 Thermal Evaporation Integrity to FET Fabrication Process Diamond:H Low Budget Temp. FET Fab. Process 14 ‐ 2 P = 1 x 10 cm MoO Thermal dep. s 3 Diamond:H S/D Contacts E‐Beam 12 ‐ 2 P = 4 x 10 cm s Ra=0.86nm Diamond:H HfO – Oxide gates ALD 150 C 2 Challenges: : 6.7 eV 5 eV Diamond:H 1. Nonhomogeneous Morphology. 2. Stoichiometry Changed by Fab. Process. 3. Carrier Loss due to band-energy Misalignment. Vardi et.al. EDL .35,12 (2014)
ALD MoO 3 Surface Acceptor ALD 170 C: Mo(CO) 6 / O 3 MoO 3 Roughness Quality improved. 1. Electronic Gap- States- reducing WF . 2. Band Energy Misalignment. Ra=0.36nm Yin & Tordjman et. al. Science Advances , 4:eaau0480,(2018).
ALD H y MoO 3 Surface Acceptor ALD 350 C: C 12 H 20 MoN 4 / H 2 O H y MoO 3 O1s XPS Mo3d XPS H MoO H MoO Y 3 Y 3 MoO MoO 3 3 Yin & Tordjman et. al. Science Advances , 4:eaau0480,(2018).
ALD H y MoO 3 Surface Acceptor ALD 350 C: C 12 H 20 MoN 4 / H 2 O H y MoO 3 Hydrogen Incorporation Contributes: 1. Strengthen Covalent bonds. No O Reduction. No Work Function Degradation. 2. Improved Surface Roughness Quality. What about Energy- Band Alignment? Ra=0.30nm Yin & Tordjman et. al. Science Advances , 4:eaau0480,(2018).
Diamond:H/MoO 3 Vs. H y MoO 3 Properties HyMoO3-x Mo3d XPS XRD HyMoO3 MoO3-x MoO3 Intensity A.U H y MoO 3-x ALD after RTA High Budget Temp. FET Fab. Process Diamond:H MoO or H MoO ALD 3 y 3 As grown H y MoO 3 ALD MoO 3-x ALD after process Diamond:H S/D Contacts E‐Beam As grown MoO 3 ALD 5 10 15 20 25 30 35 40 45 50 55 60 65 2 ( ) Diamond:H HfO – Oxide gates ALD 150 C 2 + RTA 600 C Diamond:H Top gate + Channel isolation Yin & Tordjman et. al. Science Advances , 4:eaau0480,(2018).
Diamond:H/MoO 3 Vs. H y MoO 3 FETs H MoO y 3 MoO 3 Yin & Tordjman et. al. Science Advances , 4:eaau0480,(2018).
MoO 3 Vs. H y MoO 3 Band - Energy Alignment MoO : 6.7 eV 5 eV 3 H MoO : 6 eV 5.9 eV y 3 Yin & Tordjman et. al. Science Advances , 4:eaau0480,(2018).
MoO 3 Vs. H y MoO 3 Band - Energy Alignment Yin & Tordjman et. al. Science Advances , 4:eaau0480,(2018).
Conclusions A Novel Advantageous Surface Acceptor: H y TMO General Strategy for Integrating and Modulating Electronic States in H y TMO. Diamond:H/H y MoO 3 Surface Acceptor shows: 1. Improved Morphology Smoothness . 2. Immunity to Harsh Processing FET Fab. 3. Improved Cross‐Transport via band‐energy alignment. Thank YoU
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