Intellectual Merit of the project is to demonstrate key technology toward development of novel multifunctional devices based on antiferromagnetic (AF) semiconductors. The proposed devices will combine non-volatile magnetic memory with electronic transistor functionality in a single device, thus resolving current dichotomy between logic circuitry and memory implementations. For operation devices will utilize phase transitions which, combined with sup-ps intrinsic magnetization dynamics, will offer THz speeds in both functionality domains. The devices will also have a potential to improve on basic transistor switching characteristics if gate-induced coupled phase transitions are realized. Finally, these magnetic devices will have no fringing fields, thus allowing high density packaging. The proposed devices are metal-oxide-AF-semiconductor field-effect transistors, MOS(AF)FET, where mobile carriers are induced into an AF semiconductor by electrostatic gating. This functionality will enable electrical detection of the magnetization axis in collinear AF materials for the first time. At high carrier concentrations we expect a succession of metal-insulator, antiferromagneticferromagnetic (AF-FM) and structural phase transitions, which will allow electrostatic control of both electrical and magnetic properties of the AF host. Of a special interest for fast memory recording is a possibility to rotate the magnetization axis in multi-axis collinear AF by means of AF-FM phase transition, where magnetic torque will be generated by a few tesla intrinsic exchange fields. For prototype demonstrations we will focus on NiO. NiO is a technologically relevant room temperature collinear AF semiconductor which can be epitaxially grown on readily available MgO substrates. The focus of EAGER proposal is to fabricate and characterize NiO?based MOS(AF)FET and to demonstrate electrical detection of AF magnetization axis.

The broader impact of this project will be development of the enabling technology for the investigation of electrostatically-induced AF-FM phase transition, study of fundamental physics of coupled phase transitions, and analysis of magnetization dynamics in AF semiconductors. A student working on the project will be involved in a truly interdisciplinary research, bridging fields of material science, semiconductor physics and magnetism. The PI is developing a new graduate course on physics of magnetic semiconductors which will be disseminated to a wider audience using NSF-sponsored nanoHUB.org facility at Purdue University.

Project Report

This exploratory research was aimed at a proof-of concept demonstration that electrostatic detection of magnetization in antiferromagnetic materials is possible. The major focus of research was on the development of a new technology where antiferromagnetic material is embedded into an field-effect transistor structure which will alows electrostatic induction of charges into otherwise insulating material. As a first step, we have had to develop an epitaxial growth of antiferromagnetic material NiO using pulsed laser deposition (PLD). We achieved high quality growth with sub-nm roughness and proper stoichiometry for the growth on NiO on MgO substrates. FET was developed using two complemented approaches. For all-epitaxial devices we developed a stencil mask holder which allows in situ FET growth of multi-layer patterned heterostructures. Both the holder and deep Si etching process for the mask fabrication has been developed. In parallel, we explored liquid electrolyte gating of NiO, which does not require in situ patterning and has less stringent requirements on the NiO surface quality. We succeeded in demonstrating charge control using electrolyte gating in NiO. These developments will allow investigation of antiferromagnetic materials and, specifically, their magnetic properties using electric currents, and open a possibility for these materials to be used in future multifunctional megnetic/electric devices.

Project Start
Project End
Budget Start
2012-03-15
Budget End
2014-02-28
Support Year
Fiscal Year
2012
Total Cost
$104,611
Indirect Cost
Name
Purdue University
Department
Type
DUNS #
City
West Lafayette
State
IN
Country
United States
Zip Code
47907