FORC analysis of nanopatterned vs unpatterned films: Coercivity and switching mechanisms
We have studied the use of self-assembled block copolymers to pattern multilayers of Co and Pd on silicon wafers. Stacks ranging from four to twelve bilayers of Co (0.3 nm)/Pd (0.8 nm) were sputtered onto Ta/Pd seed layers and capped with 3 nm of Ta and were found to have perpendicular magnetic anis...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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AIP Publishing LLC
2022-03-01
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| Series: | AIP Advances |
| Online Access: | http://dx.doi.org/10.1063/9.0000336 |
| _version_ | 1818394253524467712 |
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| author | Alecsander D. Mshar Allen G. Owen Daniel D. Arnold Pieter B. Visscher Randy K. Dumas Subhadra Gupta |
| author_facet | Alecsander D. Mshar Allen G. Owen Daniel D. Arnold Pieter B. Visscher Randy K. Dumas Subhadra Gupta |
| author_sort | Alecsander D. Mshar |
| collection | DOAJ |
| description | We have studied the use of self-assembled block copolymers to pattern multilayers of Co and Pd on silicon wafers. Stacks ranging from four to twelve bilayers of Co (0.3 nm)/Pd (0.8 nm) were sputtered onto Ta/Pd seed layers and capped with 3 nm of Ta and were found to have perpendicular magnetic anisotropy as-deposited. The block copolymer polystyrene-block-poly(ferrocenyl dimethylsilane) (PS-b-PFS) was dissolved in toluene and spun onto the wafers. The polymers were phase-separated by heat treatment, leaving self-assembled PFS spheres embedded in PS, which was removed by oxygen-plasma ashing. The PFS spheres were then used as masks to ion-mill the Co/Pd multilayers into nanopillars. To study the effect of etch time and etch angle on the coercivity distribution, we synthesized samples in a Design of Experiments-(DoE)- in these two factors. Scanning electron micrographs showed nanopillars ranging from 15 to 30 nm in diameter, depending primarily on etch time. M-H loops measured on both patterned and unpatterned wafers showed an increase of up to 130% in overall coercivity upon patterning. First Order Reversal Curves (FORC) were measured, and the resulting FORC distributions displayed using a smoothing program (FORCinel) and one that can display the raw data without smoothing (FORC+). We find that FORC+ reveals information about fine-scale structure and switching mechanism that cannot be seen in the smoothed display. |
| first_indexed | 2024-12-14T05:58:16Z |
| format | Article |
| id | doaj.art-5e881951c2ea4d92a7d078d5c5e70d47 |
| institution | Directory Open Access Journal |
| issn | 2158-3226 |
| language | English |
| last_indexed | 2024-12-14T05:58:16Z |
| publishDate | 2022-03-01 |
| publisher | AIP Publishing LLC |
| record_format | Article |
| series | AIP Advances |
| spelling | doaj.art-5e881951c2ea4d92a7d078d5c5e70d472022-12-21T23:14:31ZengAIP Publishing LLCAIP Advances2158-32262022-03-01123035230035230-510.1063/9.0000336FORC analysis of nanopatterned vs unpatterned films: Coercivity and switching mechanismsAlecsander D. Mshar0Allen G. Owen1Daniel D. Arnold2Pieter B. Visscher3Randy K. Dumas4Subhadra Gupta5Electrical and Computer Engineering, University of Alabama, Tuscaloosa, Alabama 35401, USAElectrical and Computer Engineering, University of Alabama, Tuscaloosa, Alabama 35401, USAComputer Science, University of Alabama at Huntsville, Huntsville, Alabama, 35899, USAPhysics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35401, USAQuantum Design, San Diego, California 92121, USAMetallurgical and Materials Engineering, University of Alabama, Tuscaloosa, Alabama 35401, USAWe have studied the use of self-assembled block copolymers to pattern multilayers of Co and Pd on silicon wafers. Stacks ranging from four to twelve bilayers of Co (0.3 nm)/Pd (0.8 nm) were sputtered onto Ta/Pd seed layers and capped with 3 nm of Ta and were found to have perpendicular magnetic anisotropy as-deposited. The block copolymer polystyrene-block-poly(ferrocenyl dimethylsilane) (PS-b-PFS) was dissolved in toluene and spun onto the wafers. The polymers were phase-separated by heat treatment, leaving self-assembled PFS spheres embedded in PS, which was removed by oxygen-plasma ashing. The PFS spheres were then used as masks to ion-mill the Co/Pd multilayers into nanopillars. To study the effect of etch time and etch angle on the coercivity distribution, we synthesized samples in a Design of Experiments-(DoE)- in these two factors. Scanning electron micrographs showed nanopillars ranging from 15 to 30 nm in diameter, depending primarily on etch time. M-H loops measured on both patterned and unpatterned wafers showed an increase of up to 130% in overall coercivity upon patterning. First Order Reversal Curves (FORC) were measured, and the resulting FORC distributions displayed using a smoothing program (FORCinel) and one that can display the raw data without smoothing (FORC+). We find that FORC+ reveals information about fine-scale structure and switching mechanism that cannot be seen in the smoothed display.http://dx.doi.org/10.1063/9.0000336 |
| spellingShingle | Alecsander D. Mshar Allen G. Owen Daniel D. Arnold Pieter B. Visscher Randy K. Dumas Subhadra Gupta FORC analysis of nanopatterned vs unpatterned films: Coercivity and switching mechanisms AIP Advances |
| title | FORC analysis of nanopatterned vs unpatterned films: Coercivity and switching mechanisms |
| title_full | FORC analysis of nanopatterned vs unpatterned films: Coercivity and switching mechanisms |
| title_fullStr | FORC analysis of nanopatterned vs unpatterned films: Coercivity and switching mechanisms |
| title_full_unstemmed | FORC analysis of nanopatterned vs unpatterned films: Coercivity and switching mechanisms |
| title_short | FORC analysis of nanopatterned vs unpatterned films: Coercivity and switching mechanisms |
| title_sort | forc analysis of nanopatterned vs unpatterned films coercivity and switching mechanisms |
| url | http://dx.doi.org/10.1063/9.0000336 |
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