2008B1925                         BL46XU⎬ X ✢శ㔚ሶಽశᴺࠍ೑↪ߒߚ࠻ࡦࡀ࡞⏛᳇ᛶ᛫ലᨐ⤑ߩࠨࡉ࠽ࡁࠝ࡯࠳࡯㗔ၞߦ߅ߌࠆࡃ࡝ࠕጀߩൻቇ⁁ᘒಽᨆChemical state analysis of barrier layer in the sub-nanometer
ranges for tunneling magnetoresistance films by hard x-ray
photoemission spectroscopy.
ᩉౝ సᤘ㧘ᐔ↰ ੩㧘ᄢᎹ ๺㚅ሶ㧘࿯ደ ⧐ᒄ
Katsuaki Yanagiuchi, Kei Hirata, Wakako Okawa, Yoshihiro Tsuchiya
TDK ᩣᑼળ␠㩷 TDK CORPORATION⎬ X ✢శ㔚ሶಽశᴺ㧔HAXPES㧕೑↪ߩ╙৻Ბ㓏ߣߒߡ‫⏛࡞ࡀࡦ࠻ޔ‬᳇ᛶ᛫ലᨐ㧔TMR㧕⚛ሶ⤑ߩᦨ਄ጀߩ଻⼔⤑ߢ޽ࠆ⤑ෘ⺞ᢛ࡞࠹࠾࠙ࡓ㧔Ru㧕⤑ߩ⤑ෘࠍᄌ߃ߚ⹜ᢱߩ᷹ቯࠍⴕߞߚ‫ޕ‬ฦర⚛ߩࠬࡍࠢ࠻࡞ᒝᐲ߆ࠄᷫ⴮㐳ߐࠍ⺞ߴ‫ޔ‬ᷓߐᣇะߩಽᨆ㗔ၞࠍ⷗Ⓧ߽ߞߚ‫ޕ‬ᰴߦࠕ࠾࡯࡞೨ᓟߩ⹜ᢱࠍ↪޿ߡ‫ࡦࡠࡏޔ‬㧔B㧕ߩൻቇ⁁ᘒ⸃ᨆࠍⴕߞߚ‫ޕ‬㊄ዻ㑆⚿วߦࠃࠆߣ⠨߃ࠄࠇࠆࠊߕ߆ߥࠤࡒࠞ࡞ࠪࡈ࠻߇᷹ⷰߐࠇ‫ޔ‬BOx ߩ↢ᚑ߹ߢߦߪ⥋ߞߡ޿ߥ޿ߎߣ߇್᣿ߒߚ‫ޕ‬ࠠ࡯ࡢ࡯࠼㧦 ⏛᳇ᄙጀ⤑‫⏛ޔ‬᳇⸥㍳‫ ⎬ޔࠬࠢ࠾ࡠ࠻ࠢ࡟ࠛࡦࡇࠬޔ‬X ✢శ㔚ሶಽశ⢛᥊ߣ⎇ⓥ⋡⊛㧦ࠬࡇࡦ࠻ࡠ࠾ࠢࠬಽ㊁ߦ߅ߌࠆ‫⏛࡞ࡀࡦ࠻ޔ‬᳇ᛶ᛫㧔TMR㧕ലᨐࠍ೑↪ߒߚࡂ࡯࠼࠺ࠖࠬࠢ࠼࡜ࠗࡉ㧔HDD㧕↪ߩౣ↢⏛᳇ࡋ࠶࠼޽ࠆ޿ߪ⏛᳇࡜ࡦ࠳ࡓࠕࠢ࠮ࠬࡔࡕ࡝㧔MRAM㧕ߢߪ‫ޔ‬㜞޿⏛᳇ᛶ᛫ലᨐࠍ␜ߔ㉄ൻࡑࠣࡀࠪ࠙ࡓ㧔MgO㧕߇ TMR ⚛ሶߩࡃ࡝ࠕጀߣߒߡ↪޿ࠄࠇߡ޿ࠆ‫ߩߎޕ‬㜞޿⏛᳇ᛶ᛫ലᨐࠍ೑↪ߒߡ‫ޔ‬HDD ↪ߩౣ↢⏛᳇ࡋ࠶࠼ߢߪ⦟ᅢߥౣ↢ᗵᐲ߇ታ⃻ߐࠇ‫ޔ‬㜞޿⸥㍳ኒᐲࠍታ⃻น⢻ߦߒߡ޿ࠆ=1?‫ޔߡߒߘޕ‬዁᧪ߩ㜞ㅦ߆ߟਇើ⊒ߥ࡜ࡦ࠳ࡓࠕࠢ࠮ࠬࡔࡕ࡝ߩ 1 ߟߣߒߡ⎇ⓥ㐿⊒߇ㅴ߼ࠄࠇߡ޿ࠆ‫ޔ‬MRAM ߦ߅޿ߡ߽㜞޿ାภኻ㔀㖸㧔SN㧕Ყࠍᓧࠆߚ߼ߦߪ‫ޔ‬㜞޿ MR Ყ߇ᔅⷐߣߥߞߡ޿ࠆ‫ޕ‬
MgO ߪ⚿᥏⾰ߢ޽ࠅ㧔100㧕ᣇะߦ⚿᥏㈩ะߒߚ⁁ᘒߦ߅޿ߡ‫ޔ‬਄ਅߦ㈩⟎ߐࠇࠆ Fe ޽ࠆ޿ߪ CoFe ߣߩࡃࡦ࠼᭴ㅧߩ⦟ᅢߥࡑ࠶࠴ࡦࠣߦࠃߞߡ‫࡞ࡀࡦ࠻࠻ࡦ࡟࡯ࡅࠦޔ‬ലᨐߦࠃࠆ㜞޿⏛᳇ᛶ᛫㧔MR㧕Ყ߇ታ⃻ߐࠇߡ޿ࠆ‫ޕ‬㜞޿ MR Ყࠍᓧࠆߚ߼ߦ Fe㧔001㧕㈩ะ⤑޽ࠆ޿ߪ CoFeB ࠕࡕ࡞ࡈࠔࠬ⤑਄ߦ MgO ࠍၸⓍߒ‫ޔ‬300͠એ਄ߩ㜞᷷ᾲಣℂࠍᣉߔߎߣ߇ႎ๔ߐࠇߡ޿ࠆ=2?=3?‫ޔߒ߆ߒޕ‬300͠એ਄ߩ㜞᷷ߢᾲಣℂࠍⴕߞߚ႐ว‫ޔ‬MgO ߣ CoFeB⇇㕙ߢߩේሶߩࡑࠗࠣ࡟࡯࡚ࠪࡦߦࠃߞߡ B ㉄ൻ‛߇↢ᚑߐࠇ=4?‫ޔ‬MR Ყૐਅߩⷐ࿃ߩ৻ߟߣߐࠇߡ޿ࠆ‫ޕ‬߹ߚ‫ޔ‬CoFeB ࠍᒝ⏛ᕈ㔚ᭂ⤑ߣߒߡ↪޿ࠆ႐วߦ໧㗴ߣߥࠆߩߪ‫ࠕ࡝ࡃޔ‬ጀ⇇㕙ߢߩ࡜ࡈࡀࠬߦ⿠࿃ߒߚ MgO ߩᰳ㒱߿‫⏛ޔ‬ᕈጀ޽ࠆ޿ߪ෻ᒝ⏛ᕈጀ߆ࠄߩࡃ࡝ࠕጀౝㇱ࡮⇇㕙߳ߩర⚛᜛ᢔߦࠃࠆ MR Ყߩૐਅߢ޽ࠆ‫ޕ‬MgO ጀߪ 1 nm એਅߩᭂ⭯⤑ߢ޽ࠅ‫߁ࠃߩߎޔ‬ߥࠨࡉ࠽ࡁࠝ࡯࠳࡯㗔ၞߩర⚛ᖱႎࠍ⺞ߴࠆᚻᴺߣߒߡ‫⿛ޔ‬ᩏဳㅘㆊ㔚ሶ㗼ᓸ㏜㧔STEM㧕ߦࠃࠆࠛࡀ࡞ࠡ࡯ಽᢔಽశᴺ㧔EDS㧕߿ࠛࡀ࡞ࠡ࡯៊ᄬಽశᴺ㧔EELS㧕‫ޔ‬エ X ✢㗔ၞߩశ
㔚ሶಽశᴺ㧔XPS㧕ࠍ↪޿ߡ᷹ቯߒߚ଀ߪ޽ࠆ߇‫⹜ޔ‬ᢱߩ૞⵾߇㔍ߒ޿ߎߣߣ‫ߩࠄࠇߎޔ‬ᚻᴺߪ TMR ⤑ࠍ᭴ᚑߔࠆฦጀࠍ㔺಴ߐߖߡൻቇ⁁ᘒಽᨆࠍⴕߞߡ޿ࠆߚ߼‫ޔ‬ᬌ಴ߐࠇࠆ
ᖱႎߪ⹜ᢱߩ‫⴫ޟ‬㕙‫ޠ‬ᖱႎࠍ฽ࠎߢ߅ࠅ‫ޔ‬ታ㓙ߩ MgO ጀౝㇱߩࡃ࡞ࠢ⊛ߥ⁁ᘒߣ⇣ߥߞߡ޿ࠆน⢻ᕈ߇޽ߞߚ‫ޕ‬
HDD ↪ߩାภౣ↢↪⏛᳇ࡋ࠶࠼ߣߒߡߪ‫ޔ‬TMR ⚛ሶߩਅㇱߦାภ⏛⇇ࠍๆ෼ߔࠆߚ߼ߩ‫ޔ‬エ⏛ᕈࠪ࡯࡞࠼߇㈩⟎ߐࠇߡ߅ࠅ‫ޔ‬300͠એ਄ߩ㜞᷷ߩᾲಣℂߦࠃߞߡ⚿᥏☸ᓘ߇⢈ᄢൻߒߡエ⏛᳇․ᕈ߇ഠൻߒߡߒ߹߁ߚ߼‫ޔ‬น⢻ߥ㒢ࠅૐ޿᷷ᐲߢߩᾲಣℂ߇ᔅⷐߣߥߞߡ޿ࠆ‫ޕ‬ᧄႎ๔ߢߪ‫ޔ‬㕖⎕უߢᄙጀ⤑ౝㇱߩൻቇ⁁ᘒࠍಽᨆߢ߈ࠆ BL46XU ߩ HAXPES ߦࠃࠆฦర⚛ߩᬌ಴ᷓߐߩផቯߣ 300͠ࠃࠅૐ޿᷷ᐲߢᾲಣℂࠍᣉߒߚ႐วߦ߅ߌࠆ B ߩൻቇ⁁ᘒࠍಽᨆߒߚ⚿ᨐߦߟ޿ߡႎ๔ߔࠆ‫ޕ‬ታ㛎㧦ࠪ࡝ࠦࡦၮ᧼਄ߦਅ࿾ጀ෻ᒝ⏛ᕈጀ࿕ቯጀ㩿CoB ࠍ฽߻⏛ᕈጀ㪀ࡃ࡝ࠕጀ㩿MgO㪀⥄↱ጀ㧔CoB ࠍ฽߻⏛ᕈጀ㧕߆ࠄߥࠆⓍጀ⤑ߦ⤑ෘ⺞ᢛߩߚ߼ߩ Ru ࠍߘࠇߙࠇ 57.610.6
13.615 nm ߩ⤑ෘߢᚑ⤑ߒߚ⹜ᢱߣߘࠇߙࠇ 300͠ࠃࠅૐ޿᷷ᐲߣߒߡ 250͠ߢࠕ࠾࡯࡞ߒߚ⹜ᢱࠍ↪ᗧߒ‫ޔ‬SPring-8BL46XU ߩ HAXPES ࠍ↪޿ߡ‫ޔ‬Ru3dCo2pB1sMg1sߩฦࠬࡍࠢ࠻࡞ࠍ᷹ቯߒߚ‫ޕ‬ ᰴߦᧄታ㛎ߩᄙጀ⤑᭴ㅧߦ߅ߌࠆฦర⚛ߩᷫ⴮㐳ߐࠍ⺞ߴࠆߚ߼ߦએਅߩᑼࠍ↪޿ߚ‫ޕ‬
2 ጀࡕ࠺࡞ߩ╙ 1 ጀߩᒝᐲߪ‫ޔ‬I§d ··§I 0¨¨1  exp¨ ¸ ¸¸ 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩿1㪀
© L cosT ¹ ¹©

ߣߥࠅ‫ ╙ޔ‬2 ጀߩᒝᐲߪ‫ޔ‬Id ·§I 0 exp¨ ¸ 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩷 㩿2㪀
© L cosT ¹

ߢ⴫ߐࠇࠆ=5?‫ޔߒߛߚޕ‬d ߪ╙ 1 ጀߩ⤑ෘ‫ ޔ‬I 0 ߪ⋡⊛ర⚛ߩጀ߇චಽߦෘ޿ߣ߈ߩᒝᐲ‫ޔ‬L ߪᷫ⴮㐳ߐ‫ޔ‬T ߪᴺ✢ߣᬌ಴ེߩߥߔⷺߢ޽ࠆ‫ ╙ޕ‬1 ጀߩ⤑ෘ d ߣ HAXPES ฦࠬࡍࠢ࠻
࡞ߩ᷹ቯᒝᐲߣߩ㑐ଥ߆ࠄ Ru ߪ㩿1㪀ᑼࠍ‫ޔ‬BMgCo ߦߟ޿ߡߪ‫ޔ‬㩿2䋩ᑼࠍ↪޿ߡ‫ᦨޔ‬ዊ
ੑਸ਼ㄭૃᴺߦࠃߞߡ‫ ޔ‬I 0 ߅ࠃ߮ L ࠍ᳞߼ߚ‫ᧄޕ‬ታ㛎ߩᄙጀ⤑⹜ᢱߦ߅ߌࠆ B1s ߩ႐วߦߟ޿ߡ‫⚿ߩࠣࡦࠖ࠹࠶ࠖࡈޔ‬ᨐࠍ Fig. 1 ߦ␜ߔ‫ޕ‬ห᭽ߦߒߡ᳞߼ߚ I 0 ߅ࠃ߮ L ࠍ Table 1 ߦ␜ߔ‫ޕ‬

Intensity (cps)㪉㪇㪇㪇d ·§I㪙㪈㫊㩷㪪㫀㫄I 0 exp ¨ ¸© L cos T ¹
I 0 2800㪈㪌㪇㪇㪈㪇㪇㪇LT㪌㪇㪇

1010 qB䇭1s䇭Intensity
B㧝sIntensity㪇㪇㪌

㪈㪇

㪈㪌㪉㪇

Ru cap thickness (nm)Fig. 1 Least-squares fitting of B1s intensity profile and intensity profile
calculated by 㩿2㪀 formulaTable 1. Calculated Initial Intensity and Attenuation length of
Ru 3d, Co 2p, B 1s and Mg 1s, respectively

I0L

Ru 3d

12300

3.0

Co 2p

46500

5.1

B 1s2800

10.0Mg 1s43500

6.1ᰴߦ᳞߼ߚ I 0 ߅ࠃ߮ L ࠍ૶ߞߡ‫ޔ‬ᄙጀ⤑⹜ᢱߩฦర⚛ߩᬌ಴ᷓߐࠍᰴߩᑼ߆ࠄផቯߒߚ‫ ޕ‬dI ·§ L cosT ln¨1  ¸© I0¹㩿3㪀

0.3 eV㩷㩷Fig. 2 B 1s spectra of annealed and non-annealed
TMR multilayer films which the thickness ofcapping Ru is 8 nm.

⚿ᨐ߅ࠃ߮⠨ኤ㧦㩿3㪀ᑼࠍ↪޿ߡផቯߒߚ Mg 1s ߩᬌ಴ᷓߐߪ‫ޔ‬13.5 nm ߢ޽ߞߚ‫⤑ޕ‬ෘ⺞ᢛ Ru ⤑ߩ⤑ෘ߇
5 nm ߩ႐วߦߪ‫ޔ‬MgO ጀߩో૕߇ᬌ಴ߐࠇߡ޿ࠆ߇‫⤑ޔ‬ෘ⺞ᢛ Ru ⤑ߩ⤑ෘ߇ 7.6 nm ߩ႐วߦߪ‫ޔ‬MgO ਄ጀߩඨಽߩߺ߇ᬌ಴ߐࠇߡ߅ࠅ‫ࠕ࡝ࡃޔ‬ጀߣ⤑ෘ⺞ᢛ Ru ⤑ߣߩ㑆ߩ⤑
ෘ 5.9 nm ߣวࠊߖߡᧄታ㛎⹜ᢱߩ႐วߦߪ‫ޔ‬MgO ߪ 13.5 nm ߩ㗔ၞ߹ߢᬌ಴น⢻ߣ್ᢿߒߚ‫ޕ‬߹ߚ‫ޔ‬B 1s ߦߟ޿ߡ߽ห᭽ߦផቯߒߚ‫⤑ޕ‬ෘ⺞ᢛ Ru ⤑ߩ⤑ෘ߇ 7.6 nm ࠃࠅ⭯޿႐วߦߪ‫ޔ‬MgO ጀߩਅߦ޽ࠆ Co‫ޔ‬B ࠍ฽߻⏛ᕈጀ߹ߢᬌ಴ߐࠇߡ޿ࠆߩߦኻߒߡ‫⤑ޔ‬ෘ⺞ᢛ Ru⤑ߩ⤑ෘ߇ 10.6 nm ߩ႐วߦߪ‫ޔ‬MgO ጀࠃࠅ਄ߦ޽ࠆ Co‫ޔ‬B ࠍ฽߻⏛ᕈጀ߹ߢߒ߆ᬌ಴ߒ
ߡ޿ߥ޿ߎߣ߇್᣿ߒߚ‫ᧄޕ‬ታ㛎⹜ᢱߩ႐วߩ B 1s ߩᬌ಴ᷓߐߪ‫ޔ‬17.6 nm ߢ޽ߞߚ‫ޕ‬⤑ෘ⺞ᢛ Ru ⤑ 10.6 nm ߩࠨࡦࡊ࡞ߦ߅ߌࠆࠕ࠾࡯࡞ಣℂ೨ᓟߩ B 1s ࠬࡍࠢ࠻࡞ࠍ Fig.2
ߦ␜ߔ‫࡞࡯࠾ࠕޕ‬ᓟߩࠬࡍࠢ࠻࡞᏷ߦ᜛߇ࠅ߇⷗ࠄࠇߚߚ߼‫ޔ‬ᵄᒻಽ㔌ࠍⴕߞߚߣߎࠈ‫ޔ‬ࠕ࠾࡯࡞೨ߩࠬࡍࠢ࠻࡞ߩࡇ࡯ࠢࠛࡀ࡞ࠡ࡯188.7 eV ߦട߃ߡ 189.0 eV ߩ㜞⚿วࠛࡀ࡞ࠡ
࡯஥ߦ 0.3 eV ࠪࡈ࠻ߒߚࡇ࡯ࠢ߇ᓧࠄࠇߚ‫ޕ‬
CoFeB/MgO Ⓧጀ⤑ࠍ 375͠ߢࠕ࠾࡯࡞ߒߚ႐ว‫ޔ‬BOx ߩ↢ᚑ߇⏕⹺ߐࠇߚ੐଀߇ႎ๔ߐ
ࠇߡ޿ࠆ[6]߇‫ޔ‬BO x ߩ႐ว‫ޔ‬B 1s XPS ࠬࡍࠢ࠻࡞߇‫ޔ‬4 eV ⒟‫ޔ‬㜞⚿วࠛࡀ࡞ࠡ࡯஥ߦࠪࡈ
࠻ߔࠆ‫⎇ᧄޔߒ߆ߒޕ‬ⓥߩ⹜ᢱߢ᷹ⷰߐࠇߚ 0.3 eV ߩࠪࡈ࠻ߪ‫ޔ‬㊄ዻ㑆⚿วߩ㆑޿ߦࠃࠆ
ߣ⠨߃ࠄࠇࠆࠊߕ߆ߥᄌൻߢ޽ࠅ‫ޔ‬250͠ ߢᾲಣℂࠍᣉߒߚ႐วߦߪ‫ޔ‬BO x ߩ↢ᚑ߹ߢߦߪ
⥋ߞߡ޿ߥ޿ߎߣ߇᣿ࠄ߆ߣߥߞߚ‫ޕ‬੹ᓟߩ⺖㗴㧦
B ߩ᜼േ‫⁁ޔ‬ᘒᄌൻߦട߃ߡ MgO ⤑ਛ߅ࠃ߮⇇㕙ߩ᭴ㅧࠍ᣿ࠄ߆ߦߔࠆߎߣ߇‫ޔ‬㜞޿MR Ყࠍᜬߟ TMR ⚛ሶࠍ⸳⸘ߔࠆ਄ߢߪ‫ޔ‬ᭂ߼ߡ㊀ⷐߢ޽ࠆ‫੹ޕ‬ᓟ‫ޔ‬HAXPES ߩ᷹ቯ♖ᐲߩะ਄ࠍ࿑ࠆߣߣ߽ߦ੹࿁ᓧࠄࠇߚ⍮⷗ࠍၮߦ⤑ෘ⺞ᢛ Ru ⤑ߩ⤑ෘߩᦨㆡൻࠍⴕ޿‫ޔ‬ታ㛎ࠍ⛮⛯ߒߡ޿߈ߚ޿ߣ⠨߃ߡ޿ࠆ‫ޕ‬ෳ⠨ᢥ₂㧦
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