Reflectometry with Polarized Neutrons on In Situ Grown Thin Films

Abstract

Originating from the demand for obtaining depth‐resolved magnetization profiles from thin films and heterostructures, polarized neutron reflectometry (PNR) has developed into a unique research tool, which also finds application in the analysis of superconducting or soft matter thin films. While certain in situ sample environments such as gas‐loading or humidity cells were quickly realized after PNR first emerged, preparing and growing thin magnetic films directly in the neutron beam could only be realized in recent years. Herein, a dedicated insight is given on the history and development of in situ thin film growth capabilities for PNR, from early pioneering experiments to the present day. The scientific and technological challenges as well as the advances of neutron sources, neutronics, and data treatment that have led to its realization are highlighted together with the unique research opportunities that it provides and recently obtained experimental results.

Topical Review of Quantum Materials and Heterostructures Studied by Polarized Neutron Reflectometry

“…The growing ability to conduct PNR in vacuum deposition systems will also allow the technique to progressively expand into the pure surface science regime. [ 151 ] Despite their immense value as a structural and magnetic probe, neutrons are not ideal for probing electronic structures, which are an essential aspect in advanced electronic materials. Therefore, we anticipate a growing number of studies combining PNR with electronic surface measurement techniques such as ARPES and STM.…”

Phase Reconstruction of a Cu(001) Seed Layer from $\textit{in situ}$ Polarized Neutron Reflectometry Data using Fe Reference Layers

“…Subsequently, a 7 nm thick Fe thin film was added on the Cu layer in 28 deposition steps with a growth rate of approximately one monolayer of Fe per deposition step. PNR measurements are carried out after each deposition step; after the 14th deposition, only every second step is monitored by PNR [19]. The deposition and PNR measurements were performed on the neutron reflectometer Amor at the Swiss Spallation Neutron Source (SINQ), Paul Scherrer Institut, Villigen [20].…”

“…The top Fe layer represents the reference, however the Fe layer thickness is constrained and a part of it (remnant Table I. Fitted parameters of the Fe reference layer and of the unknown layer (from [19]).…”

“…Each reflectivity measurement R ± i has a corresponding reference layer SLD ± i which is used for the reconstruction of the reflection. In situ thin film growth allows the thickness of the deposited Fe layer to be known a-priori, however, the parameters used for describing the SLD of the Fe reference layer were extracted using a traditional fitting method [19]. These are listed in Table I for R 14 -R 28 .…”

Influence of Sputtering Pressure on the Micro-Topography of Sputtered Cu/Si Films: Integrated Multiscale Simulation

“…In addition, the high electrical conductivity and ultrahigh strength of gradient nanotwinned Cu films suggest their promising application in advanced micro/nanoelectromechanical systems (MEMS) [9,10]. Recently, epitaxial Cu films on Si substrates have attracted considerable research interest for their potential application in spintronic and superconducting devices [11][12][13]. Many methods have been employed to fabricate Cu/Si films, including thermal evaporation [14], electrodeposited [15], electron beam evaporation [16], and magnetron sputtering [17][18][19].…”