Multi-Bit Memories Using a Structure of Sio2/Partially-Oxidized Amorphous Si/Hfo2

Supplementary Information:

Nonvolatile memories using deep traps formed in Al2O3 by metal ion implantation

Min Choul Kim,1 Seung Hui Hong,1 Hye Ryong Kim,1 Sung Kim,1 Suk-Ho Choi,1* R. G. Elliman,2 & S. P. Russo3

1Department of Applied Physics, College of Natural Sciences, Kyung Hee University, Yongin 449-701, Korea. 2Electronic Materials Engineering Department, Research School of Physical Sciences and Engineering, Australian National University, Canberra ACT 0200, Australia 3Department of Applied Physics, School of Applied Sciences, RMIT University, Melbourne, Australia.

Contents

Figure S1 SIMS profiles of a Si/SiO2/Al2O3 structure implanted with 70 keV V ions to a dose of 1014 cm-2 and subsequently annealed at 800 oC for 1 min. Figure S2 SIMS profiles of LE-V cell with a dose of 1014 cm-2. Figure S3 Cross-sectional STEM image of the same sample used in Figure S1. Figure S4 XPS spectra of HE-Nb cell with a dose of 1016 cm-2. Figure S5 Electronic DOS for the undoped, V-doped, and Nb-doped lattices. Figure S6 Schematic diagram showing the calculated impurity energy levels for Ta doped Al2O3. Figure S7 Memory window-vs-voltage plots for HE cells with different Nb and V doses. Figure S8 C-V hysteresis loops of LE-Ru cells with different Ru doses. Figure S9 C-V hysteresis loops of LE-Ta cells with different Ta doses. Figure S10 P/E characteristics of LE-V cells with doses of 1014 and 1015 cm-2 and a LE- Nb cell with a dose of 1014 cm-2. Figure S11 Retention characteristics of LE-V cells with different doses. The retention data are extrapolated to 10 years for each level.

METHODS of theoretical calculations Figure S1 SIMS profiles of a Si/SiO2/Al2O3 structure implanted with 70 keV V ions to a dose of 1014 cm-2 and subsequently annealed at 800 oC for 1 min.

Figure S2 SIMS profiles of LE-V cell with a dose of 1014 cm-2. The implantation was done with 50 keV. Figure S3 Cross-sectional STEM image of the same sample used in Figure S1.

Figure S4 (a) XPS spectra of HE-Nb cell with a dose of 1016 cm-2 after successive Ar sputtering etching. The implantation was done with 80 keV. (b) Resolved XPS spectra obtained at depth positions of 32 and 46 nm from the surface of Al2O3 and among them, the latter one is actually from the Si substrate, judging from the absence of the Nb-O XPS components. (c) Nb-O and Nb XPS peaks as functions of depth from the surface of

Al2O3. Figure S5 Total and atom-projected eDOS for the undoped, V-doped, and Nb-doped lattices. Both the spin-up (+ y-axis) and spin-down (- y-axis) eDOS results are shown. The atom-projected contributions to the eDOS from the dopant atoms (V/Nb) are shown in blue while those from the nearest neighbour Al and O atoms are shown in red and green respectively. Figure S6 Schematic diagram showing the calculated impurity energy levels for Ta doped Al2O3.

Figure S7 Memory window-vs-voltage plots for HE cells with different Nb and V doses. The implantations were done with 70 and 100 keV for V and Nb ions, respectively.

Figure S8 C-V hysteresis loops of memory cells containing Ru ions of 1012 and 1013 cm- 2 doses. The implantation was done with 80 keV.

Figure S9 C-V hysteresis loops of memory cells containing Ta ions of 1012 - 1014 cm-2 doses. The implantation was done with 110 keV.

Figure S10 P/E characteristics of LE-V cells with doses of 1014 and 1015 cm-2 and a LE- Nb cell with a dose of 1014 cm-2. The implantations were done with 50 and 80 keV for V and Nb ions, respectively.

Figure S11 Retention characteristics of LE-V cells with different doses. The retention data are extrapolated to 10 years for each level. The implantation was done with 50 keV. METHODS of theoretical calculations

Spin unrestricted hybrid Density Functional calculations were performed [1] using the CRYSTAL software suite [1] which is based on the periodic, linear combination of atomic orbitals (LCAO) formalism where the Bloch orbitals of the crystals are expanded using atom centred Gaussian orbitals with s, p or d symmetry, (f symmetry polarisation functions can also be used). Becke's three parameter hybrid functional (B3LYP) [2] was used for the treatment of electron exchange and correlation in the calculations. Within this approximation, exchange and correlation is given by:

LDA HF B88 LYP VWN E XC  (1 a0 )E X  a0 E X  a X E X  ac EC  (1 ac )EC

B88 HF where ax E X is Becke's gradient correction to the exchange functional, E X is the

Hartree-Fock-exchange energy, and the correlation is given by a combination of the

Lee, Yang and Parr (LYP) and the Vosko, Wilk and Nussair functionals. Values for a0, ax and ac are 0.2, 0.72 and 0.81 respectively, as given by Becke [2]. Solid state calculations using this functional have been shown to yield band structure [3] and structural properties [4] in excellent agreement with experiment.

Each of the Al and O atoms were represented by 8-511d1G and 8-411d1G basis sets respectively (18 atomic orbitals for each atom). These basis sets were optimised for  -

Al2O3 bulk structure [5]. The dopant atoms V and Nb were represented by 86-411d4G [6] and 986-31d631G basis sets respectively. For a 5th row element such as Nb , relativistic effects in the core electrons become important. Therefore to check the accuracy of the Nb all electron basis set we compared our results to that using an effective core potential (ECP) for Nb, where the core orbitals [Ar]3d10 were replaced by a Hay and Wadt small core ECP [7,8]. The eDOS results obtained for Nb using the all electron basis-set and the ECP were within 40 meV of each other. The reciprocal space integration was performed by sampling the Brillouin zone using the Monkhorst-Pack scheme with a shrinking factor of at least 6.

References 1. CRYSTAL06 http://www.crystal.unito.it/ 2. A. D. Becke, Density-functional thermochemistry. III. The role of exact exchange. J. Chem. Phys. 98, 5648 (1993). 3. J. Muscat, A. Wander, and N. M. Harrison, On the prediction of band gaps from hybrid functional theory. Chem. Phys. Lett. 342, 397 (2001). 4. N. Wilson and J. Muscat, The calculation of structural, elastic and phase stability properties of minerals using first principles techniques: a comparison of HF, DFT and Hybrid functional treatments of exchange and correlation. J. Mol. Sim. 28, 903 (2002). 5. M. Catti, G. Valerio, R. Dovesi, and M. Causa, Quantum-mechanical calculation of the solid-state equilibrium MgO +  -Al2O3  MgAl2O4. Phys. Rev. B 49, 14179 (1994). 6. W. C. Mackrodt, N. M. Harrison, V. R. Saunders, N. L. Allan, M. D. Towler, E. Apra', and R. Dovesi, Ab initio Hartree-Fock calculations of CaO, VO, MnO and NiO. Philos. Mag. A 68, 653 (1993). 7. P. J. Hay and W. R. Wadt, Ab initio effective core potentials for molecular calculations. Potentials for K to Au including the outermost core orbitals. J. Chem. Phys. 82, 299 (1985). 8. S. Dall'Olio, R. Dovesi, and R. Resta, Spontaneous polarization as a Berry phase of

the Hartree-Fock wave function: The case of KNbO3. Phys. Rev. B 56, 10105 (1997).