WO2017204202A1 - Oxyde semi-conducteur - Google Patents

Oxyde semi-conducteur Download PDF

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WO2017204202A1
WO2017204202A1 PCT/JP2017/019148 JP2017019148W WO2017204202A1 WO 2017204202 A1 WO2017204202 A1 WO 2017204202A1 JP 2017019148 W JP2017019148 W JP 2017019148W WO 2017204202 A1 WO2017204202 A1 WO 2017204202A1
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oxide semiconductor
oxide
semiconductor
type
pyrochlore structure
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PCT/JP2017/019148
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English (en)
Japanese (ja)
Inventor
直人 菊地
相浦　義弘
浩史 川中
瑞平 王
浩 高島
朱音 三溝
紳太郎 池田
外岡　和彦
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国立研究開発法人産業技術総合研究所
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Publication of WO2017204202A1 publication Critical patent/WO2017204202A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G35/00—Compounds of tantalum

Definitions

  • the present invention relates to an oxide semiconductor composed of an oxide composite, and more particularly to an oxide semiconductor capable of realizing p-type semiconductor characteristics.
  • transparent conductor materials and transparent semiconductor materials having high transparency in the visible light region and high electrical conductivity are known as oxide composites, and are widely used for transparent electrodes and the like.
  • transparent semiconductors In 2 O 3 , ZnO, SnO 2 , and Sn-added In 2 O 3 , impurities added to these base materials, Al-added ZnO, Ga-added ZnO, Sb-added SnO 2 , and F-added SnO are used. 2 and the like are known, but these are all n-type semiconductors in which electrons serve as charge carriers.
  • semiconductors include p-type semiconductors that use holes as charge carriers. If n-type and p-type semiconductors that are transparent in the visible light region are prepared, forming a pn junction makes it possible to produce a diode, transistor, solar cell, or the like that is transparent in the visible light region.
  • Cu 2 O, NiO, and the like are already known as p-type semiconductors, but are not transparent because they absorb light in the visible light region and have strong coloration. Since 1990, research and development of transparent p-type conductors has been promoted, and several new transparent p-type conductors have been reported.
  • a compound having a delafossite structure has low hole mobility.
  • the oxychalcogenide compound has a considerably high mobility and hole concentration, but is oxidized in the air atmosphere, so that the characteristic deterioration is remarkable.
  • zinc oxide is an n-type semiconductor that originally uses electrons as charge carriers, it is necessary to reduce the concentration of structural defects that generate electrons to the limit and introduce structural defects that express p-type semiconductor characteristics such as nitrogen. There is. For this reason, it is difficult to produce zinc oxide having p-type semiconductor characteristics and poor reproducibility due to the difficulty in generating n-type structural defects accompanying the introduction of p-type structural defects and reducing the concentration of n-type structural defects. Therefore, it is difficult to realize a transparent p-type semiconductor suitable for an electronic device.
  • An oxide semiconductor is expected as a semiconductor material resistant to an oxidation reaction in an atmosphere containing oxygen.
  • it is difficult to realize p-type conductivity with an oxide. This is because in the oxide, electrons at the upper end of the valence band are localized on oxygen ions.
  • a metal d-orbital component is introduced at the upper end of the valence band
  • a p-orbital component of a chalcogen element is introduced at the upper end of the valence band. The presence is reduced.
  • Non-Patent Document 1 a metal oxide having a pyrochlore structure represented by a composition formula Sn 2 Ta 2 O 7 is composed of a 5s component of Sn at the upper end of the valence band.
  • Patent Document 2 reports a photocatalyst of an oxide complex composed of Sn 2 Nb 2 O 7 (oxide semiconductor) and titanium oxide.
  • the photocatalyst is composed of an oxide composite having a junction made of different kinds of oxide semiconductors having different energy levels of electrons at the bottom of the conduction band and electrons at the top of the valence band.
  • Ta is listed as an option similar to Nb.
  • Patent Document 3 discloses ABO 4 + x (where ⁇ 0.25 ⁇ x ⁇ 0.5, A ions are Sn elements, B ions are one or more elements selected from Nb and Ta), and fluorite. Pyrochlore-related structure in which oxygen vacancies are regularly present and oxygen vacancies in the pyrochlore structure where cations are regularly arranged are filled with oxygen, either ⁇ -PbO 2 -related structures or rutile-related structures A photocatalyst having a structure has been reported.
  • Non-Patent Document 3 reports that Sn 2 Nb 2 O 7 having a pyrochlore structure does not develop a photocatalyst, whereas Sn 2 Ta 2 O 7 having the same pyrochlore structure has a weak photocatalytic activity.
  • the present invention is intended to solve these problems, and an object of the present invention is to provide a novel oxide semiconductor that has low light absorption in the visible light region and can realize high charge carrier mobility. And It is another object of the present invention to provide an oxide semiconductor that exhibits p-type semiconductor characteristics.
  • the present invention has the following features in order to achieve the above object.
  • the present invention relates to an oxide semiconductor, and is composed of an oxide composite having a crystal structure including Sn and Ta and including at least a pyrochlore structure, and a composition ratio Sn / Ta is 0.60 ⁇ Sn / Ta ⁇ 1.0. It is characterized by being.
  • the oxide semiconductor of the present invention is characterized in that holes serve as charge carriers.
  • a transparent and high mobility semiconductor having a wide gap can be realized in an oxide semiconductor.
  • a p-type oxide semiconductor was realized by the oxide semiconductor of the present invention.
  • the p-type is realized by generating the structural defect V ′′ Sn.
  • the composition ratio Sn / Ta is 0.60 or more, it takes a crystal structure including at least a pyrochlore structure.
  • the oxide semiconductor of the present invention is composed of a 5s component of Sn at the upper end of the valence band.
  • the semiconductor of the present invention is made of an oxide and has weather resistance
  • an electronic device having excellent weather resistance can be realized by forming a pn junction of the p-type oxide semiconductor and the n-type oxide semiconductor of the present invention. .
  • the oxide semiconductor of the present invention has at least a pyrochlore structure containing Sn and Ta having a band gap of 3.0 eV, and when Ta 2 O 5 coexists slightly, the band gap of Ta 2 O 5 Is 4.0-4.5 eV, a wide gap can be realized and high transparency is obtained in the visible light region.
  • complex in 1st Embodiment. is there. It is a figure which shows the change of the specific resistance with respect to the analysis composition value (Sn / Ta) after in 1st Embodiment. It is a figure which shows the change of the density
  • the present inventor conducted research and development by paying attention to the fact that semiconductor characteristics are influenced by the composition ratio of Sn / Ta in an oxide composite having a pyrochlore structure, and has excellent semiconductor characteristics. Thus, an oxide semiconductor having semiconductor characteristics has been obtained.
  • SnO having a small bandgap in which the upper end portion of the valence band is composed of 5s orbitals of Sn is bonded to ions by forming a double oxide with Ta 2 O 5.
  • the crystal structure has at least a pyrochlore structure, and the Sn / Ta composition ratio Sn / Ta is 0.60 ⁇ It is a semiconductor with Sn / Ta ⁇ 1.0.
  • the oxide semiconductor according to the embodiment of the present invention is Sn 2 Ta 2 O 7 having a small composition with respect to the stoichiometric composition ratio so as to form holes that are p-type charge carriers.
  • Non-Patent Document 2 in a compound described as Sn 2 Ta 2 O 7 with a simple composition formula, if two structural defects are represented, Sn 2-x (Ta 2-y Sn y ) O 7-x-0.5y .
  • these two structural defects are V ′′ Sn and Sn ′ Ta , respectively, according to the Crager-Bink notation, and both are structural defects having negative charges. Therefore, when these defects are generated, it is considered that any of them becomes a center of a structural defect that causes generation of holes. That is, less than the stoichiometric composition, that is, Sn / Ta ⁇ 1 indicates a structural defect represented by V ′′ Sn .
  • No oxide composite having a pyrochlore structure has developed p-type semiconductor characteristics, including Non-Patent Document 2 above. It generates a -2 valence defect V '' Sn simultaneously generates +2 oxygen vacancy V ⁇ ⁇ O, so resulting in charge compensation, the expression of p-type conduction is not obtained due to holes generated Therefore, it is considered.
  • the amount of V ′′ Sn and V ⁇ O produced is considered to depend on the temperature and the atmospheric gas conditions when the oxide composite is produced. In the present invention, the generation of V ′′ Sn is controlled by changing the composition ratio Sn / Ta at the time of sample preparation, while V ⁇ O appropriately controls the atmospheric gas conditions.
  • n-type semiconductor suitable for forming a pn junction with the p-type semiconductor of this embodiment In 2 O 3 , ZnO, SnO 2 , Sn-doped In 2 O 3 in which impurities are added to these base materials, Al adding ZnO, Ga added ZnO, Sb added SnO 2, F added SnO 2.
  • ZnO is preferable from the standpoints that, in addition to the feature that it is possible to fabricate from an insulator to a semiconductor due to easy control of the carrier concentration, there is no problem of etching and easiness of patterning and the scarcity of raw materials.
  • an oxide semiconductor including an oxide composite including Sn and Ta and having at least a pyrochlore structure will be described.
  • the characteristics corresponding to the composition ratio Sn / Ta were examined.
  • the composition ratio Sn / Ta is 0.81 ⁇ Sn / Ta ⁇ 1.0, indicating a single phase of the pyrochlore structure, and 0.60 ⁇ Sn / Ta ⁇ 0.81, and the pyrochlore structure and Ta 2 O 5 Shows a coexisting crystal structure.
  • Ta 2 O 5 coexists in the crystal structure by a maximum of 25%.
  • p-type semiconductor characteristics using holes as charge carriers are exhibited at 0.60 ⁇ Sn / Ta ⁇ 1.0.
  • the band gap of Ta 2 O 5 exhibits 4.0 to 4.5 eV.
  • the oxide semiconductor embodiment of the present invention at least has the pyrochlore structure containing Sn and Ta which is the band gap showing the 3.0 eV, if further slightly coexist Ta 2 O 5 is the wide gap Ta 2 Since it contains O 5 , a wide gap can be realized even if it is not a single phase with a pyrochlore structure, and it has high transparency in the visible light region.
  • Example 1 Weighed SnO powder (purity 99.5%, Purity Chemical Laboratory Co., Ltd.) and Ta 2 O 5 (purity 99.9% Purity Chemical Laboratory, Inc.) into an agate mortar and added ethanol (Japanese Wet mixing was carried out for about 1 hour while adding Kogyo Pharmaceutical Co., Ltd. special grade). At this time, SnO and Ta 2 O 5 were mixed so that the ratio of Sn to Ta (Sn / Ta) was 0.60, 0.70, 0.80, and 1.00 in terms of atomic ratio. This charged composition value is hereinafter referred to as “(Sn / Ta) before ”. Table 1 summarizes the amount of reagent weighed during sample preparation.
  • the mixture was allowed to stand overnight at room temperature to dry the ethanol, and the powder divided into approximately six equal parts was uniaxially pressed (diameter: 15 mm, 170 MPa) to produce six disk-shaped green compacts.
  • the green compact was placed on an alumina boat, placed in an electric furnace having an alumina furnace tube having a diameter of 50 mm and a length of 800 mm, and pre-baked at 900 ° C. for 4 hours while flowing a nitrogen gas at a flow rate of 150 ml / min.
  • the calcined green compact was crushed in an agate mortar, and an aqueous polyvinyl alcohol solution as a binder was 2 wt. % And mixed with ethanol and left to dry overnight at room temperature.
  • the particle size was adjusted to 212 ⁇ m or less by sieving, and uniaxial pressing (diameter: 15 mm, 170 MPa) followed by hydrostatic pressing (285 MPa) to produce a molded body having a diameter of about 15 mm and a thickness of about 1.2 mm.
  • the obtained molded body was placed on an alumina boat and subjected to main firing at 750 ° C. for 4 hours while flowing nitrogen gas (flow rate: 50 ml / min).
  • Sample Nos. 1 to 4 have a charge composition value ((Sn / Ta) before ) of 0.60, 0.70, 0.80, and 1.00, respectively, and nitrogen during firing. This is a sample prepared under the condition of a gas (N 2 gas) flow rate of 50 ml / min.
  • Example 1 [Analytical composition value and electrical property of oxide composite having pyrochlore structure containing Sn and Ta]
  • the crystal structure of the sample obtained in Example 1 was identified by an X-ray diffractometer (Panalytic X'Pert Pro MRD).
  • a wavelength dispersive X-ray fluorescence analyzer (Rigaku ZSX) was used.
  • the analytical composition value after firing is expressed as “(Sn / Ta) after ”.
  • the evaluation of the electrical characteristics of the sample was performed using a Hall effect measuring device (Toyo Technica Resitest 8310) with a van der Pau arrangement prepared by depositing gold electrodes on the four corners of a circular sample.
  • the Seebeck coefficient of the sample was evaluated using a thermoelectric property evaluation apparatus (Advanced Riko ZEM-3). All measurements were performed at room temperature.
  • FIG. 1 shows changes in the X-ray diffraction pattern of the Sn 2 Ta 2 O 7 sample in Example 1 by (Sn / Ta) after .
  • the horizontal axis in FIG. 1 is the diffraction angle 2 ⁇ with respect to the incident angle ⁇ using CuK ⁇ rays.
  • a peak attributed to Sn 2 Ta 2 O 7 having a pyrochlore structure belonging to a cubic system shown by a black circle (222)) (400) (440) (622) etc.
  • Table 2 shows the analytical composition value (Sn / Ta) after and electrical measurement results (specific resistance, concentration of charge carrier, mobility, Seebeck coefficient) for samples prepared by changing the charged composition value ((Sn / Ta) before ).
  • FIG. 2 shows a change in specific resistance with respect to (Sn / Ta) after .
  • the nitrogen flow rate at the time of firing in Table 2 is 50 ml / min.
  • the case of producing under the conditions (white circle) is shown.
  • the error bar in the figure indicates the standard deviation ⁇ .
  • FIG. 2 shows specific resistance values in Table 2 in the range of (Sn / Ta) after of about 0.60 to about 1.0 (specifically 0.998).
  • the specific resistance of the sample is (Sn / Ta) after in this range from 5 ⁇ 10 1 to 4 ⁇ 10 2 ⁇ cm, and both exhibit electrical conductivity.
  • FIG. 3 shows changes in the concentration of the charge carrier with respect to (Sn / Ta) after .
  • the error bar indicates the standard deviation ⁇ .
  • the concentration of the charge carrier increases as (Sn / Ta) after decreases. It can be seen that it has increased. This is presumably because Sn in the pyrochlore structure was deficient and Sn vacancies V ′′ Sn were generated by the decrease in Sn / Ta. Since Sn vacancies V ′′ Sn are defects that generate carrier holes, it is considered that the concentration of holes, which are charge carriers of the p-type semiconductor, increased as V ′′ Sn increased.
  • thermoelectric property evaluation apparatus shown in Table 2 all showed positive values. This indicates that all of sample numbers 1 to 4 in Example 1 have holes as charge carriers.
  • the composition ratio Sn / Ta it is clear that when p is 0.60 ⁇ Sn / Ta ⁇ 1.0, it exhibits a p-type semiconductor characteristic having a crystal structure including at least a pyrochlore structure and using holes as charge carriers.
  • Thin-film oxide semiconductors can be produced by sputtering, heating, electron beam deposition, ion plating, and other oxide film production methods such as spin coating and spray coating using solutions as starting materials. Can be manufactured by technology.
  • the oxide semiconductor of the present invention can realize a p-type semiconductor, a pn junction can be realized by an n-type semiconductor and a p-type semiconductor that are transparent in the visible light region, and widely used in devices such as a transmissive display and a transparent transistor. Can be industrially useful.

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  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)

Abstract

L'invention porte sur un oxyde semi-conducteur possédant une transparence, une mobilité et une résistance aux intempéries excellentes, avec lequel il est possible de réaliser un semi-conducteur de type p dans un oxyde semi-conducteur. On a obtenu un oxyde semi-conducteur possédant une structure de pyrochlore comprenant Sn et Ta, et le rapport Sn/Nb de composition 0.60 ≤ Sn/Ta < 1,0. L'oxyde semi-conducteur présente une bande interdite large d'environ 3.0 eV et est donc un semi-conducteur de type p présentant une transparence dans la région de la lumière visible et une mobilité élevée. Lorsque la quantité de Sn est faible par rapport à la composition stoechiométrique de la formule de composition Sn2Ta2O7, c'est-à-dire lorsque Sn/Ta < 1, un type p peut être réalisé par la génération d'un défaut structural V''Sn, et une structure de pyrochlore est obtenue lorsque le rapport de composition Sn/Ta est d'au moins 0.60.
PCT/JP2017/019148 2016-05-25 2017-05-23 Oxyde semi-conducteur WO2017204202A1 (fr)

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JP2016-104471 2016-05-25

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58219703A (ja) * 1982-06-01 1983-12-21 イ−・アイ・デユ・ポン・ドウ・ヌム−ル・アンド・カンパニ− 酸化錫を含む導電相の製造方法

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58219703A (ja) * 1982-06-01 1983-12-21 イ−・アイ・デユ・ポン・ドウ・ヌム−ル・アンド・カンパニ− 酸化錫を含む導電相の製造方法

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
MASAO KITA ET AL.: "a -Pb02-retated phase appearing in the SnIV-Ta-0 system transformed from cation-ordered fluorite-related phase", JOURNAL OF THE CERAMIC SOCIETY OF JAPAN, vol. 122, no. 1430, October 2014 (2014-10-01), pages 902 - 907, XP055600322 *
MASAO KITA ET AL.: "Synthesis of novel cation-ordered compounds with fluorite-related structure prepared by oxidation of Sn-Ta-0 pyrochlore", JOURNAL OF SOLID STATE CHEMISTRY, vol. 178, no. 4, April 2005 (2005-04-01), pages 1254 - 1261, XP004866195 *
W. BIEGER ET AL.: "Thermodynamic investigations in the system Sn-Ta- 0", MATERIALS SCIENCE FORUM, vol. 62 - 64, 1990, pages 325 - 327 *

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