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Hydrogen induced dipole at the Pt/oxide interface in MOS devices
Author(s) -
Kolomiiets Nadiia M.,
Afanas'ev Valeri V.,
Opsomer Karl,
Houssa Michel,
Stesmans Andre
Publication year - 2016
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201532413
Subject(s) - work function , materials science , oxide , fermi level , platinum , analytical chemistry (journal) , hydrogen , electron , annealing (glass) , optoelectronics , chemistry , nanotechnology , layer (electronics) , physics , metallurgy , biochemistry , organic chemistry , quantum mechanics , chromatography , composite material , catalysis
Thanks to its good thermal stability, including resistance to oxidation, platinum (Pt) is widely used in prototyping a wide spectrum of electron devices ranging from metal‐oxide‐semiconductor (MOS) transistors to resistive switching memory cells. In this work, the energy barriers for electrons between the Fermi level of Pt and the conduction band of several oxide insulators (SiO 2 , Al 2 O 3 , HfO 2 , Hf 0.8 Al 0.2 O x , Sr 0.53 Ti 0.47 O 3 ) were determined by using internal photoemission of electrons. By combining this barrier value with the electron affinity of the particular oxide, the effective work function (EWF) of Pt was determined for different interfaces. As studied over the reference Pt/oxide/Si stacks de‐gassed in high vacuum at 400 °C, the EWF of Pt is found to differ significantly from the accepted vacuum WF value of 5.6 eV. The EWF is equal to 5.2 eV at the Pt/Al 2 O 3 interface, 5.1 eV at Pt/HfO 2 , 5.3 eV at Pt/Hf 0.8 Al 0.2 O x , 4.8 eV at Pt/SiO 2 , and 5.8 eV at the Pt/Sr 0.53 Ti 0.47 O 3 interface indicating the presence of a polarization layer of which the contribution to the EWF depends on the oxide composition. Furthermore, annealing in H 2 at 400 °C reduces the Pt EWF by ∼0.5 eV at all interfaces except for the Pt/Sr 0.53 Ti 0.47 O 3 one. This observation indicates the formation of an additional H‐related dipole at the Pt/oxide interfaces and suggests that the vacuum WF of Pt cannot be used as the value relevant for the MOS properties.