Crystalline oxide thin film, multilayer body and thin film transistor
A crystalline oxide thin film contains an In element, a Ga element and an Ln element, in which the In element is a main component, the Ln element is at least one element selected from the group consisting of La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and an average crystal grain size D 1 is in a range from 0.05 μm to 0.5 μm.
1. A crystalline oxide thin film comprising: an In element, a Ga element, and a Ln element, wherein
the In element is a main component,
the Ln element is at least one element selected from the group consisting of La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and
the crystalline oxide thin film comprises an average crystal grain size D 1 in a range from 0.05 μm to 0.5 μm, wherein
an average grain-boundary angle θ formed between a thin film surface of the crystalline oxide thin film and crystal grain boundaries inside the crystalline oxide thin film is in a range from 70 degrees to 110 degrees.
2. The crystalline oxide thin film according to claim 1 , wherein
an average interval D 2 between crystal grain boundaries inside the crystalline oxide thin film is in a range from 0.05 μm to 0.40 μm.
3. The crystalline oxide thin film according to claim 1 , wherein
in a plane TEM-EDS analysis on the crystalline oxide thin film, metal elements forming the crystalline oxide thin film are not segregated in the crystal grain boundaries inside the crystalline oxide thin film.
4. The crystalline oxide thin film according to claim 1 , wherein
ranges of atomic composition ratios represented by formulae (1), (2) and (3) are satisfied,
0.85<In/(In+Ga+Ln)≤0.98 (1)
0.01≤Ga/(In+Ga+Ln)<0.11 (2)
0.01≤Ln/(In+Ga+Ln)<0.04 (3).
5. The crystalline oxide thin film according to claim 1 , wherein
the crystalline oxide thin film comprises crystal grains with a Bixbyite structure in electron beam diffraction of the crystalline oxide thin film.
6. The crystalline oxide thin film according to claim 1 , wherein the Ln element is a Sm element.
7. A thin film transistor comprising: electrodes; and a crystalline oxide thin film, wherein
the crystalline oxide thin film comprises an In element, a Ga element and a Ln element,
the In element is a main component of the crystalline oxide thin film,
the Ln element is at least one element selected from the group consisting of La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu,
the electrodes comprise a source electrode, a drain electrode, and a gate electrode; and
in a cross-sectional TEM observation of the thin film transistor, a contact region length Ls between (a) the source electrode or the drain electrode and (b) the crystalline oxide thin film and an average interval D 2 between crystal grain boundaries inside the crystalline oxide thin film satisfy relationships of a formula (4) and a formula (5),
1 μm≤ Ls≤ 50 μm (4)
10≤ Ls/D 2 ≤1000 (5).
8. The thin film transistor according to claim 7 , wherein
an average crystal grain size D 1 in the crystalline oxide thin film is in a range from 0.05 μm to 0.5 μm.
9. The thin film transistor according to claim 7 , wherein
an average grain-boundary angle θ formed between a thin film surface of the crystalline oxide thin film and the crystal grain boundaries inside the crystalline oxide thin film is in a range from 70 degrees to 110 degrees, and
an average interval D 2 between the crystal grain boundaries inside the crystalline oxide thin film is in a range from 0.05 μm to 0.40 μm.
10. A thin film transistor comprising: a crystalline oxide thin film, wherein
the crystalline oxide thin film comprises an In element, a Ga element, and a Ln element,
the In element is a main component,
the Ln element is at least one element selected from the group consisting of La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu,
an average crystal grain size D 1 in the crystalline oxide thin film is in a range from 0.05 μm to 0.5 μm,
an average grain-boundary angle θ formed between a thin film surface of the crystalline oxide thin film and crystal grain boundaries inside the crystalline oxide thin film is in a range from 70 degrees to 110 degrees, and
an average interval D 2 between the crystal grain boundaries inside the crystalline oxide thin film is in a range from 0.05 μm to 0.40 μm.
11. The thin film transistor according to claim 10 , wherein
in a plane TEM-EDS analysis on the crystalline oxide thin film, metal elements forming the crystalline oxide thin film are not segregated in the crystal grain boundaries inside the crystalline oxide thin film.
12. The thin film transistor according to claim 10 , wherein
ranges of atomic composition ratios represented by formulae (1), (2) and (3) are satisfied,
0.85<In/(In+Ga+Ln)≤0.98 (1)
0.01≤Ga/(In+Ga+Ln)<0.11 (2)
0.01≤Ln/(In+Ga+Ln)<0.04 (3).
13. The thin film transistor according to claim 10 , wherein
the crystalline oxide thin film comprises crystal grains with a Bixbyite structure in electron beam diffraction.
14. The thin film transistor according to claim 10 , wherein
the Ln element is a Sm element.
15. A crystalline oxide thin film comprising: an In element, a Ga element, and a Ln element, wherein
the In element is a main component,
the Ln element is at least one element selected from the group consisting of La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and
the crystalline oxide thin film comprises an average crystal grain size D 1 in a range from 0.05 μm to 0.5 μm, wherein an average interval D 2 between crystal grain boundaries inside the crystalline oxide thin film is in a range from 0.05 μm to 0.40 μm.
16. The crystalline oxide thin film according to claim 15 , wherein
in a plane TEM-EDS analysis on the crystalline oxide thin film, metal elements forming the crystalline oxide thin film are not segregated in the crystal grain boundaries inside the crystalline oxide thin film.
17. The crystalline oxide thin film according to claim 15 , wherein
ranges of atomic composition ratios represented by formulae (1), (2) and (3) are satisfied,
0.85<In/(In+Ga+Ln)≤0.98 (1)
0.01≤Ga/(In+Ga+Ln)<0.11 (2)
0.01≤Ln/(In+Ga+Ln)<0.04 (3).
18. The crystalline oxide thin film according to claim 15 , wherein
the crystalline oxide thin film comprises crystal grains with a Bixbyite structure in electron beam diffraction of the crystalline oxide thin film.
19. The crystalline oxide thin film according to claim 15 , wherein the Ln element is a Sm element.
20. A laminate comprising:
the crystalline oxide thin film according to claim 15 ; and
a support supporting the crystalline oxide thin film, wherein
an average grain-boundary angle θsub formed between a surface of the support and crystal grain boundaries inside the crystalline oxide thin film is in a range from 70 degrees to 110 degrees.