Mark Kimbell Prof. Takoudis Manish Singh Yi Yang

 Chemical Vapor Deposition  Nickel Oxide (NiO) using Ni(C 5 H 5 ) 2  Iron Oxide (Fe 2 O 3 ) using FeC 14 H 18  Nickel Ferrite (NiFe 2 O 4 ) ▪ Choose appropriate conditions based on NiO and Fe 2 O 3 growth rates ▪ XPS to analyze chemical composition ▪ XRD to analyze crystalline structure

 The magnetoelectric (ME) effect  Ferroelectric and ferromagnetic coupling ▪ Magnetic switching by an applied electric field ▪ Electric polarity switching by an applied magnetic field

 Uses  Memory storage devices  Tunable microwave devices  Sensors  Transducers C Israel, ND Mathur & JF Scott, Nature Materials 7 (2008) 93

 Magnetoelectric composites  Made up of a piezoelectric layer and a magnetostrictive layer NiFe 2 O 4

Argon gas Oxygen gas Quartz tube Heater Vacuum pump Substrate

 Source of the vapor which is fed into the reaction chamber NICKELOCENE  Ni(C 5 H 5 ) 2 N-BUTYLFERROCENE  C 14 H 18 Fe

Nickel Oxide Data 8 Nickel Oxide Growth Rate (Reactor = 400 o C) Temperature of Nickelocene ( o C)

9 Iron Oxide Data Temperature of N-Butylferrocene ( o C) Growth Rate (nm/min) Iron Oxide Growth Rate (Reactor = 500 o C)

 T reactor = 400 o C  T nickelocene = 60 o C  T reactor = 400 o C  T n-butylferrocene = 65 o C NiO growth rate = 4.6 nm/min Fe 2 O 3 growth rate = 8.5 – 9 nm/min

Cycles T nickelocene T n-butylferrocene T reactor NiO deposition time (s)Fe 2 O 3 deposition time (s)Cycles Co-deposition T nickelocene T n-butylferrocene T reactor Deposition time (min)

 Uses x-rays to knock electrons free from surface  Measures kinetic energy of electrons to determine chemical composition

 Longer cycles (5 cycles, 90 seconds each) ElementAtomic Conc. (%) Ni23.13 Fe27.30 O37.31 C12.27 Ni 2p Fe 2p O 1s C 1s

 Shorter cycles (20 cycles, 18 seconds each) ElementAtomic Conc. (%) Ni24.82 Fe28.81 O39.40 C6.97 Ni 2p Fe 2p O 1s C 1s

 Co-Deposition ElementAtomic Conc. (%) Ni26.50 Fe22.69 O30.29 C20.52 Ni 2p Fe 2p O 1s C 1s T nickelocene T n-butylferrocene T reactor 60 o C65 o C400 o C

 Co-Deposition ElementAtomic Conc. (%) Ni29.17 Fe22.11 O31.07 C17.65 Ni 2p Fe 2p O 1s C 1s T nickelocene T n-butylferrocene T reactor 60 o C 400 o C

Peaks correspond to Fe(III) oxidation state * S. A. Chambers, Y. J. Kim, and Y. Gao Surf. Sci. Spectra (1998) *

* A. N. Mansour, Surf. Sci. Spectra (1994) Peaks correspond to Ni(II) oxidation state *

 Do not indicate the presence of NiFe 2 O 4  Probably due to interactions between the two gases  Presence of carbon  From atmosphere ▪ Argon sputtering  From unreacted precursor ▪ Due to relatively low deposition temperature

 XPS revealed the presence of both Ni(II) and Fe(III)  The ratio of Ni to Fe did not indicate NiFe 2 O4  Different deposition conditions must be used in order to achieve the correct ratios  Higher reactor temperature  Higher iron precursor temperature  Lower nickel precursor temperature

 Try different deposition conditions to deposit NiFe 2 O 4 thin films  X-ray diffraction (XRD) on NiFe 2 O 4 thin films to determine crystalline structure  Anneal to reduce carbon contamination, correct defects / change crystal structure

 E. Ascher, H. Rieder, H. Schmid, and H. Stössel, J. Appl. Phys. 37 (1966) 1404  W. Eerenstein, N. D. Mathur and J. F. Scott, Nature 442, (2006)  A.M.J.G. Van Run, D.R. Terrell, and J.H. Scholing, Journal of Materials Science 9 (1974)  W. Yeh and M. Matsumura, Jpn. J. Appl. Phys. Vol. 36 (1997) Pt. 1, No. 11  M. Singh, Y. Yang, and C.G. Takoudis, Journal of The Electrochemical Society, 155 (9) (2008) D618-D623  S.A. Chambers, Y.J. Kim, and Y. Gao, Surf. Sci. Spectra 5 (1998) 219  S. Oswald and W. Bruckner, Surf. Interface Anal. 36 (2004) 17–22  XPS.htm

 EEC-NSF Grant #  Dr. Christos Takoudis  Graduate students: Yi Yang, Manish Singh, Qian Tao

Argon gas Oxygen gas Quartz tube Heater Vacuum pump Substrate Cycling

Argon gas Oxygen gas Quartz tube Heater Vacuum pump Substrate Co-Deposition

Temperature controllers Precursor containers Reaction chamber Cold trap Vacuum pump nickelocene n-butylferrocene

 Used to measure film thickness Light source Polarizer Sample Analyzer Θ