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A study of ion beam modification of CoMnNiO amorphous films
Nuclear Instruments North-Holland
and Methods
in Physics
Research
B59/60
7x5
(1991) 785-787
A study of ion beam modification of C~Mn~iO
a~o~hous
films
Tan Hui, Tao Mingde, Qin Dong and Han Ying Xinjlang Institute
of Physics, Academia
Sinica, Urumqi 830011. Xinjiang,
Lin Chenglu and Zhou Zuyao fun BeamL&orator?; Shanghai institute of
Metaliurgy.
Academia
China
Sinica, Shanghai 2~OS0,
China
CoMnNiO amorphous film is a thermally sensitive material with negative temperature samples are deposited on an oxidized Si substrate by means of rf sputtering. The samples cm.-2 Cu+ and 100 keV. 1 X lOI cmP2 Mg+ ions, respectively, and thermally annealed The experimental results indicate that the resistivity of Cu+ and Mg+ implanted samples lower than that of unimplant~ samples. When annealed above 600°C. the resist&&y increasing annealing temperature due to the formation of a Cu cubic spine1 solid solution
coefficient. In this study. CoMnNiO film are then implanted with 360 keV. 1 x 10” at XK-900°C for 4 h in O2 atmosphere. annealed at temperatures below 550 o C is of Cu+ implanted films decreases with having relatively good conducti~ty. When annealed above 900°C, part of the cubic spine1 is resolved and low-valence oxides such as CuO, COO, and NiO are produced, while the resistivity of the film samples is increased. When Mg+ implanted film is annealed above 600” C, its resistivity increases, but when annealed above 900°C, its resistivity decreases obviously, in the same way as conventional thermally sensitive material including Mg. It is also shown that Cu+ and Mg’. implantation of the CoMnNiO films can improve the electrical properties and the linearity of resistance-temperature characteristics of the films. Using ion beam modification, an applicable temperature sensitive
material having a wide operating range can be obtained.
1. Introduction
2. Experiment
film deposited by rf sputtering is a practical material for the production of thermistors having negative temperature coefficient. The resistivity of CoMnNiO amorphous film is generally 1.3 x IO* Q cm. After annealing at 500°C, the resistivity of the sample can be increased up to 1 x lo3 fZ cm. In order to procure a material having a wide operating range of temperature, the resistivity of the amorphous film should be decreased. A good method to decrease the resistivity of the film is to introduce metal ions into the amorphous film. Ion beam modifications of transition metal oxide amorphous film have been reported [1,2]. Koshida et al. [l] examined the dependence of sheet resistance of amorphous film on the implanted dose and discovered the transition of insulator-metal [3]. However, studies on ion beam modification of CoMnNiO amorphous film have not been reported yet. We studied the change of electrical properties with annealing temperature in CoMnNiO amorphous film implanted by Cut or Mg+; this article describes and discusses our experimental results. Amorphous
CoMnNiO
0168-583X/91/$03.50
CoMnNiO films are deposited on an oxidized Si substrate using rf sputtering. The target for sputtering is a sintered material in oxygen atmosphere of a mixture of Co, Mn, Ni, having the ratio 3 : 2 : 1. The film exhibits an amorphous structure [4]. The amorphous film is implanted by 360 keV, 1 X 1On’ cm-’ Cu’ and 100 keV, 1 X lOI cm-’ Mg+ ions, respectively. These samples are cut into 4 x 8 mm* small pieces and annealed in oxygen atmosphere for 4 h at 500, 700, 800. and 900 o C, respectively. Analyses are made using resistance measurements and the X-ray diffraction method. The electrical properties and structural characteristics of the CoMnNiO films are studied. 3. Results and discussion Fig. 1 shows the spreading resistance of the specimens with and without Cu+ implantation annealed at various temperature. It is found that when the annealing temperature is below 9OO’C. the spreading resistance of the specimens implanted by Cu+ is lower than that of the specimen without implantation. When the annealing temperature is 900°C, the spreading resis-
0 1991 - Elsevier Science Publishers B.V. (North-Holland)
VII. METALS
,‘TRlBOLOGY
5z 0
1 DEPTH
DEPTH
(um)
Fig. 1. Spreading resistance of the amorphous film samples annealed at various temperatures. Solid lines represent the samples implanted by Cu+, dashed lines represent the unimplanted samples. tance of the implanted films is slightly higher than that of the unimplanted films. Experimental results also indicate that when the annealing temperature is below 600 o C, a structural relaxation of CoMnNiO amorphous fiim will occur [S]. In the structural relaxation, the defects in the film are annealed. This causes an increase in the resistance of the film. The implantation of metal ions into the film can improve its conductivity. Thus, the resistance of the amorphous films implanted by Cu+ is lower than that of the unimplanted film. The temperature range of 600-800” C is the crystallizing temperature of the amorphous film [S]. In the process of crystallization, the structure of amorphous film is transformed gradually into a cubic spine1 solid solution with increasing annealing temperature. In fact, the multicompositional film is a series of spine1 solutions. Typical conductivity of the cubic spine1 solid solution containing Cu is about 10-‘-10-3 0-l cm-*, which is higher than that of the one without Cu component. Thus when the film is annealed at the temperature range of 600800°C. the spreading resistance of the film implanted by Cut is lower than that of the unimplanted specimen. When the film is annealed at a temperature above 900°C. the spine1 solid solution in the film is resolved into the subvalence oxides COO, CuO, NiO, having poor electrical conductivity. Consequently, the resistance of the amorphous film is increased. Since spine1 solid solution with Cu has a lower resolving temperature, the resistance of the specimens implanted by Cu+
(urn)
Fig. 2. Spreading resistance of the amorphous film samples annealed at various temperatures. Solid tines represent the samples implanted by Mg’, dashed lines represent the unimplanted samples.
is higher than that of the specimens unimplanted. The spreading resistance of CoMnNiO amorphous films with and without Mg+ implantation annealed at various temperatures is shown in fig. 2. It is seen that the resistance of the film implanted by Mg+ is lower than that of the unimplanted films. When the annealing temperature is 7OO”C, the amorphous films are transformed into crystallized ones. which decreases the resistance of the films. During the process of crystallization, valence-variable ions, Co, Mn and Ni, in the films are rapidly transformed into a spine1 solid solution. Thus the resistance of the films implanted by Mg+ is lower
As-deposited
70
60
I
I
1
50
40
30
2t! Fig. 3. X-ray diffraction patterns of the CoMnNiO amorphous films before and after annealing in 0, atmosphere at various temperatures (see ref. [5] for identification of peaks).
Tan Hui et al. / CoMnNiO amorphou films
than that of the films without Mg+ implantation. When annealed at 800 o C, the effect of the oxygen absorption in the film is enhanced, and dissociative Mg is transformed into MgO. Resistance of the film implanted by Mg+ is much higher than that of the unimplanted films because of the poor conduction of MgO. When annealed at 900 o C, part of the spine1 solid solution formed by Co, Mn and Ni in the films is dissociated, which causes an increase of the resistance of the films. Because the spine1 solid solution containing Mg is very stable and cannot be dissociated at 900 o C, thus, the resistance of the films implanted by Mg+ is lower than that of the unimplanted films. The X-ray diffraction patterns of CoMnNiO amorphous films before and after annealing at various temperatures are shown in fig. 3. It is shown that the structure of the film before annealing is amorphous. When it is annealed at 550° C, there are some microcrystals in the films. When annealed above 600°C crystallization is enhanced significantly, indicating the formation of a series of cubic spinels of solid solution Co[MnCo_,Ni, _,]O, [5]. CoMnNiO amorphous film is a p-type semiconductor. The conductivity of the material is dependent on the exchange of electrons between valence-variable positive ions. The conductivity of transition metal oxide is due to the transition of carriers between energy levels instead of the motion of the carriers in the valence band. It can be described by the small polaron model. Exchange of valence variable ions in transition metal oxide can be written as follows: Ni’++
Ni”+
Nizf+
Ni3+,
co3++
co2+--+ co2++
co3+,
Mn4++ Mn3++ Mnz++ Co-“-
181
It is well known that the conductivity of a material is dependent on the concentration and drift mobility of the carriers. In fact, metal ion implantation into amorphous CoMnNiO can increase the carrier concentration, increasing the conductivity of the material. The temperature coefficient of the CoMnNiO amorphous film material is less dependent on temperature than that of polycrystal or simple compositional amorphous materials. When metal ions are implanted into the CoMnNiO amorphous film, multinetworks included implantation metal ions are formed in the film. These networks are compensating each other, linearizing the resistance-temperature characteristic. Multinetworks compensation is expected to be a effective method for the production of a linear temperature transducer.
References
Ul N. Koshida and 0. Tomita, Jpn. J. Appl. Phys. 25 (1988) 1932.
PI N. Koshida, Y. Ichinose and K. Ohtaka, Nucl. Instr. and Meth. B39 (1989) 736. [31 N. Koshida and Y. Iketsu, Jpn. J. Appl. Phys. 26 (1987) 1596.
141 Tan Hui, Tao Mingde, Han Ying and Zhang Han, Chin. J. Semiconduct.
10 (1989) 497. and Han duct. 10 (1989) 721.
[51 Tan Hui. Tao Mingde
Ying,
Chin.
J. Semicon-
Mn3++ Mn4’, Co”+
Mn3+, etc.
VII. METALS
,’ TRIBOLOGY
and Methods
in Physics
Research
B59/60
7x5
(1991) 785-787
A study of ion beam modification of C~Mn~iO
a~o~hous
films
Tan Hui, Tao Mingde, Qin Dong and Han Ying Xinjlang Institute
of Physics, Academia
Sinica, Urumqi 830011. Xinjiang,
Lin Chenglu and Zhou Zuyao fun BeamL&orator?; Shanghai institute of
Metaliurgy.
Academia
China
Sinica, Shanghai 2~OS0,
China
CoMnNiO amorphous film is a thermally sensitive material with negative temperature samples are deposited on an oxidized Si substrate by means of rf sputtering. The samples cm.-2 Cu+ and 100 keV. 1 X lOI cmP2 Mg+ ions, respectively, and thermally annealed The experimental results indicate that the resistivity of Cu+ and Mg+ implanted samples lower than that of unimplant~ samples. When annealed above 600°C. the resist&&y increasing annealing temperature due to the formation of a Cu cubic spine1 solid solution
coefficient. In this study. CoMnNiO film are then implanted with 360 keV. 1 x 10” at XK-900°C for 4 h in O2 atmosphere. annealed at temperatures below 550 o C is of Cu+ implanted films decreases with having relatively good conducti~ty. When annealed above 900°C, part of the cubic spine1 is resolved and low-valence oxides such as CuO, COO, and NiO are produced, while the resistivity of the film samples is increased. When Mg+ implanted film is annealed above 600” C, its resistivity increases, but when annealed above 900°C, its resistivity decreases obviously, in the same way as conventional thermally sensitive material including Mg. It is also shown that Cu+ and Mg’. implantation of the CoMnNiO films can improve the electrical properties and the linearity of resistance-temperature characteristics of the films. Using ion beam modification, an applicable temperature sensitive
material having a wide operating range can be obtained.
1. Introduction
2. Experiment
film deposited by rf sputtering is a practical material for the production of thermistors having negative temperature coefficient. The resistivity of CoMnNiO amorphous film is generally 1.3 x IO* Q cm. After annealing at 500°C, the resistivity of the sample can be increased up to 1 x lo3 fZ cm. In order to procure a material having a wide operating range of temperature, the resistivity of the amorphous film should be decreased. A good method to decrease the resistivity of the film is to introduce metal ions into the amorphous film. Ion beam modifications of transition metal oxide amorphous film have been reported [1,2]. Koshida et al. [l] examined the dependence of sheet resistance of amorphous film on the implanted dose and discovered the transition of insulator-metal [3]. However, studies on ion beam modification of CoMnNiO amorphous film have not been reported yet. We studied the change of electrical properties with annealing temperature in CoMnNiO amorphous film implanted by Cut or Mg+; this article describes and discusses our experimental results. Amorphous
CoMnNiO
0168-583X/91/$03.50
CoMnNiO films are deposited on an oxidized Si substrate using rf sputtering. The target for sputtering is a sintered material in oxygen atmosphere of a mixture of Co, Mn, Ni, having the ratio 3 : 2 : 1. The film exhibits an amorphous structure [4]. The amorphous film is implanted by 360 keV, 1 X 1On’ cm-’ Cu’ and 100 keV, 1 X lOI cm-’ Mg+ ions, respectively. These samples are cut into 4 x 8 mm* small pieces and annealed in oxygen atmosphere for 4 h at 500, 700, 800. and 900 o C, respectively. Analyses are made using resistance measurements and the X-ray diffraction method. The electrical properties and structural characteristics of the CoMnNiO films are studied. 3. Results and discussion Fig. 1 shows the spreading resistance of the specimens with and without Cu+ implantation annealed at various temperature. It is found that when the annealing temperature is below 9OO’C. the spreading resistance of the specimens implanted by Cu+ is lower than that of the specimen without implantation. When the annealing temperature is 900°C, the spreading resis-
0 1991 - Elsevier Science Publishers B.V. (North-Holland)
VII. METALS
,‘TRlBOLOGY
5z 0
1 DEPTH
DEPTH
(um)
Fig. 1. Spreading resistance of the amorphous film samples annealed at various temperatures. Solid lines represent the samples implanted by Cu+, dashed lines represent the unimplanted samples. tance of the implanted films is slightly higher than that of the unimplanted films. Experimental results also indicate that when the annealing temperature is below 600 o C, a structural relaxation of CoMnNiO amorphous fiim will occur [S]. In the structural relaxation, the defects in the film are annealed. This causes an increase in the resistance of the film. The implantation of metal ions into the film can improve its conductivity. Thus, the resistance of the amorphous films implanted by Cu+ is lower than that of the unimplanted film. The temperature range of 600-800” C is the crystallizing temperature of the amorphous film [S]. In the process of crystallization, the structure of amorphous film is transformed gradually into a cubic spine1 solid solution with increasing annealing temperature. In fact, the multicompositional film is a series of spine1 solutions. Typical conductivity of the cubic spine1 solid solution containing Cu is about 10-‘-10-3 0-l cm-*, which is higher than that of the one without Cu component. Thus when the film is annealed at the temperature range of 600800°C. the spreading resistance of the film implanted by Cut is lower than that of the unimplanted specimen. When the film is annealed at a temperature above 900°C. the spine1 solid solution in the film is resolved into the subvalence oxides COO, CuO, NiO, having poor electrical conductivity. Consequently, the resistance of the amorphous film is increased. Since spine1 solid solution with Cu has a lower resolving temperature, the resistance of the specimens implanted by Cu+
(urn)
Fig. 2. Spreading resistance of the amorphous film samples annealed at various temperatures. Solid tines represent the samples implanted by Mg’, dashed lines represent the unimplanted samples.
is higher than that of the specimens unimplanted. The spreading resistance of CoMnNiO amorphous films with and without Mg+ implantation annealed at various temperatures is shown in fig. 2. It is seen that the resistance of the film implanted by Mg+ is lower than that of the unimplanted films. When the annealing temperature is 7OO”C, the amorphous films are transformed into crystallized ones. which decreases the resistance of the films. During the process of crystallization, valence-variable ions, Co, Mn and Ni, in the films are rapidly transformed into a spine1 solid solution. Thus the resistance of the films implanted by Mg+ is lower
As-deposited
70
60
I
I
1
50
40
30
2t! Fig. 3. X-ray diffraction patterns of the CoMnNiO amorphous films before and after annealing in 0, atmosphere at various temperatures (see ref. [5] for identification of peaks).
Tan Hui et al. / CoMnNiO amorphou films
than that of the films without Mg+ implantation. When annealed at 800 o C, the effect of the oxygen absorption in the film is enhanced, and dissociative Mg is transformed into MgO. Resistance of the film implanted by Mg+ is much higher than that of the unimplanted films because of the poor conduction of MgO. When annealed at 900 o C, part of the spine1 solid solution formed by Co, Mn and Ni in the films is dissociated, which causes an increase of the resistance of the films. Because the spine1 solid solution containing Mg is very stable and cannot be dissociated at 900 o C, thus, the resistance of the films implanted by Mg+ is lower than that of the unimplanted films. The X-ray diffraction patterns of CoMnNiO amorphous films before and after annealing at various temperatures are shown in fig. 3. It is shown that the structure of the film before annealing is amorphous. When it is annealed at 550° C, there are some microcrystals in the films. When annealed above 600°C crystallization is enhanced significantly, indicating the formation of a series of cubic spinels of solid solution Co[MnCo_,Ni, _,]O, [5]. CoMnNiO amorphous film is a p-type semiconductor. The conductivity of the material is dependent on the exchange of electrons between valence-variable positive ions. The conductivity of transition metal oxide is due to the transition of carriers between energy levels instead of the motion of the carriers in the valence band. It can be described by the small polaron model. Exchange of valence variable ions in transition metal oxide can be written as follows: Ni’++
Ni”+
Nizf+
Ni3+,
co3++
co2+--+ co2++
co3+,
Mn4++ Mn3++ Mnz++ Co-“-
181
It is well known that the conductivity of a material is dependent on the concentration and drift mobility of the carriers. In fact, metal ion implantation into amorphous CoMnNiO can increase the carrier concentration, increasing the conductivity of the material. The temperature coefficient of the CoMnNiO amorphous film material is less dependent on temperature than that of polycrystal or simple compositional amorphous materials. When metal ions are implanted into the CoMnNiO amorphous film, multinetworks included implantation metal ions are formed in the film. These networks are compensating each other, linearizing the resistance-temperature characteristic. Multinetworks compensation is expected to be a effective method for the production of a linear temperature transducer.
References
Ul N. Koshida and 0. Tomita, Jpn. J. Appl. Phys. 25 (1988) 1932.
PI N. Koshida, Y. Ichinose and K. Ohtaka, Nucl. Instr. and Meth. B39 (1989) 736. [31 N. Koshida and Y. Iketsu, Jpn. J. Appl. Phys. 26 (1987) 1596.
141 Tan Hui, Tao Mingde, Han Ying and Zhang Han, Chin. J. Semiconduct.
10 (1989) 497. and Han duct. 10 (1989) 721.
[51 Tan Hui. Tao Mingde
Ying,
Chin.
J. Semicon-
Mn3++ Mn4’, Co”+
Mn3+, etc.
VII. METALS
,’ TRIBOLOGY