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Micromachined epitaxial colossal mognetoresistors for uncooled infrared bolometer
KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

High quality perovskite manganites, La1-xAxMnO3 (A = Ca, Sr, Ba) are very attractive materials due to their great application potential for magnetic memory, uncooled infrared (IR) microbolometer and spintronics devices. This thesis presents studies of the growth and material characterization (including structural, electrical, magnetic and noise) of epitaxial manganite films on Si and GaAs. Furthermore, investigations about strain effect on structural and electrical properties of manganites, and finally fabrication of self-supported free standing microstructures for uncooled IR bolometer are also demonstrated.

To obtain high quality epitaxial manganite films on semiconductor substrates at room temperature, using a combination of La0.67Sr0.33MnO3 (LSMO) and La0.67Ca0.33MnO3 (LCMO) compounds, La0.67(Sr,Ca)0.33MnO3 (LSCMO) films were successfully grown on Si substrates with Bi4Ti3O12(BTO)/CeO2/YSZ buffers by pulsed laser deposition (PLD) technique. Crystallographic relations between layers shows cube-on-cube for BTO/CeO2/YSZ/Si and diagonal-on-side for LSCMO films on BTO layer. 4.4 %K-1 maximum temperature coefficient of resistivity (TCR = 1/ρ·dρ/dT) and 2.9 %kOe-1 colossal magnetoresistance (CMR) were obtained at room temperature. Assuming of a prototype of temperature sensor, 1.2 μK/√Hz of noise equivalent temperature difference (NETD) and 2.9×108 cm√Hz/W of detectivity are expected to achieve at 294 K, 30 Hz. For GaAs substrates, using MgO buffer layer, LCMO films shows 9.0 %K-1 of TCR at 223 K while LSMO exhibits 2 %K-1 at 327 K.

Systematic strain effects on structural and electrical properties of La0.75Sr0.25MnO3 LSMO) films on BTO/CeO2/YSZ-buffered Si, Si1-xGex/Si (compressive strain, x = 0.05-0.20) and Si1-yCy/Si (tensile, y = 0.01) were investigated. The strain induced from Si1-xGex/Si and Si0.99C0.01/Si has a tendency to decrease the roughness of CMR films compared to Si sample. High resistivity and low TCR values are observed for Si0.8Ge0.2/Si and Si0.99C0.01/Si samples due to excessive strains whereas Si0.9Ge0.1/Si and Si0.95Ge0.05/Si show slight improvements of films quality and TCR value.

To fabricate LSCMO manganite bolometer on Si, wet etching with KOH and BHF and dry etching methods with Ar ion beam etching (IBE) were studied. For KOH wet etching, LSCMO films show high chemical resistance with lower than 0.2 nm/min of etch rate. BHF wet etching shows high etching selectivity over photoresist mask and silicon substrates. The etch rates for LSCMO and BTO layers are 22 and 17 nm/min. For Ar IBE, LSCMO films and oxide buffer layers show similar etch rates, 16-17 nm/min that are lower compared to 24 nm/min for Si.

Free standing, self-supported heteroepitaxial LSCMO/BTO/CeO2/YSZ membranes for bolometer pixels on Si was successfully fabricated by Ar IBE and ICP etching techniques using a preannealed photoresist. The structural investigation by TEM revealed the sharp interfaces between layers. The electrical property of the free standing membrane was slightly degraded due to strain release and multi-step etching effect. These results demonstrate feasibility to use heteroepitaxial oxide structures as a thermally isolated membrane with conventional photoresist patterning.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , xvi, 78 p.
Series
Trita-EKT, ISSN 1650-8599 ; 2005:5
Keyword [en]
La0.67(Sr, Ca)0.33MnO3 (LSCMO), La0.67Sr0.33MnO3 (LSMO)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-535OAI: oai:DiVA.org:kth-535DiVA: diva2:14337
Public defence
2005-12-09, Sal C1, KTH-Electrum, 10:00
Opponent
Supervisors
Note
QC 20101101Available from: 2005-01-02 Created: 2005-01-02 Last updated: 2010-11-01Bibliographically approved
List of papers
1. Epitaxial colossal magnetoresistive La-0.67(Sr,Ca)(0.33)MnO3 films on Si.
Open this publication in new window or tab >>Epitaxial colossal magnetoresistive La-0.67(Sr,Ca)(0.33)MnO3 films on Si.
2003 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 82, no 24, 4295-4297 p.Article in journal (Refereed) Published
Abstract [en]

La-0.67(Sr,Ca)(0.33)MnO3 (LSCMO) films have been grown by a pulsed-laser deposition technique on Si(001) substrates buffered with Bi4Ti3O12/CeO2/yttrium-stabilized zirconia (YSZ) heteroepitaxial layers. X-ray diffraction has revealed cube-on-cube growth of an epitaxial Bi4Ti3O12/CeO2/YSZ/Si heterostructure whereas the LSCMO layer grows in the diagonal-on-side manner on top of the Bi4Ti3O12 (BTO) template. The maximum temperature coefficient of resistivity (TCR)=4.4% K-1 and colossal magnetoresistance (CMR) Deltarho/rhosimilar to2.9% kOe(-1) have been reached at 294 K. This was achieved due to the successive improvement of c-axis orientation of the layers: Full widths at half-maximum 0.65degrees, 0.58degrees, 0.65degrees, 1.13degrees, and 0.18degrees in LSCMO/BTO/CeO2/YSZ/Si stack, respectively. As a prototype of an uncooled bolometer, heteroepitaxial CMR structure on Si demonstrates, at 294 K, the noise equivalent temperature difference of 1.2 muK/rootHz@30 Hz.

Keyword
pulsed-laser deposition, thin-films, uncooled bolometer, growth
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-22577 (URN)10.1063/1.1583133 (DOI)000183467500028 ()
Note
QC 20100525Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2017-12-12Bibliographically approved
2. Epitaxial colossal magnetoresistive/ferroelectric heterostructures on Si
Open this publication in new window or tab >>Epitaxial colossal magnetoresistive/ferroelectric heterostructures on Si
2004 (English)In: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 67, 69-76 p.Article in journal (Refereed) Published
Abstract [en]

We report on processing and properties of La-0.67(SrCa)(0.33)MnO3 (LSCMO) films grown by pulsed laser deposition technique on Si(001) substrates buffered with Bi4Ti3O12/CeO2/YSZ heteroepitaxial layers. X-ray diffraction shows cube-on-cube growth of epitaxial Bi4Ti3O12/CeO2/YSZ/Si heterostructure whereas the LSCMO layer grows in the diagonal-on-side manner onto the Bi4Ti3O12 (BTO) template. High resolution TEM images demonstrate sharp interfaces between the buffer layers and LSCMO film as well as rare misfit dislocations on the CeO2/YSZ interface. LSCMO film processing conditions have been optimized to get maximum temperature coefficient of resistivity TCR = 4.4% K-1 and colossal magnetoresistance (CMR) Deltarho/rho similar to 2.9% kOe(-1) @ 294 K. Almost ultimate CMR performance at room temperature has been achieved due to successive improvement of c-axis orientation of layers: full widths at half-maximum (FWHM) = 0.65, 0.58, 0.65, 1.13 and 0.18 degrees in LSCMO/BTO/CeO2/YSZ/Si stack, respectively. Characterization of electrical noise in CMR film yields Noise Equivalent Temperature Difference (NETD) as low as 1.2 muK/rootHz @ 30 Hz and 294 K.

Keyword
pulsed-laser deposition, thin-films, growth
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-23987 (URN)000226089900009 ()2-s2.0-33745743275 (Scopus ID)
Note
QC 20100525Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2017-12-12Bibliographically approved
3. Microfabricated heteroepitaxial oxide structures on silicon for bolometric arrays
Open this publication in new window or tab >>Microfabricated heteroepitaxial oxide structures on silicon for bolometric arrays
2005 (English)In: 2005 NSTI Nanotechnology Conference and Trade Show - NSTI Nanotech 2005 Technical Proceedings, Anaheim, CA, 2005, 521-524 p.Conference paper, Published paper (Refereed)
Abstract [en]

The microfabrication of the free standing perovskite La0.67(Sr, Ca)0.33 MnO3 (LSCMO) thin films on silicon substrates with epitaxial grown oxide buffer layers was investigated for microbolometer application. The Ar ion etching (IBE) rate of LSCMO films was found to be 16 nm/min. Using pre-annealed photoresist patterning, the free standing LSCMO pixels on epitaxial buffer oxide membrane were realized by the IBE and SF 6 inductive coupled plasma (ICP) etching process. These results can be utilized as thermally isolated membrane for heteroepitaxial oxide structures.

Place, publisher, year, edition, pages
Anaheim, CA: , 2005
Keyword
Bolometer, La<sub>0.67</sub>(Sr, Ca)<sub>0.33</sub>Mno<sub>3</sub> (LSCMO), Membrane, Micromachining, Si, Arrays, Bolometers, Epitaxial growth, Substrates, Thin films, Buffer layers, Heteroepitaxial oxide, Silicon
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-25790 (URN)2-s2.0-32044472787 (Scopus ID)0976798522 (ISBN)
Conference
2005 NSTI Nanotechnology Conference and Trade Show - NSTI Nanotech 2005; Anaheim, CA; 8 May 2005 through 12 May 2005
Note
QC 20101101Available from: 2010-11-01 Created: 2010-11-01 Last updated: 2010-11-01Bibliographically approved
4. Free-standing epitaxial La1-x(Sr,Ca)(x)MnO3 membrane on Si for uncooled infrared microbolometer.
Open this publication in new window or tab >>Free-standing epitaxial La1-x(Sr,Ca)(x)MnO3 membrane on Si for uncooled infrared microbolometer.
2005 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 87, no 3Article in journal (Refereed) Published
Abstract [en]

Ar ion beam etching and inductively coupled SF6 and C4F8 plasma-etching processes have been employed to fabricate free standing membrane from the heteroepitaxial La1-x(Sr,Ca)(x)MnO3(50 nm)/Bi4Ti3O12(100 nm)/CeO2(40 nm)/YSZ(30 nm) film structure pulsed laser deposited on Si(001) wafer. We demonstrate feasibility to use epitaxial colossal magnetoresistive manganite film as thermally isolated self-supporting membrane for uncooled infrared microbolometer applications.

Keyword
pulsed-laser deposition, thin-films, colossal magnetoresistance, silicon, growth
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-14920 (URN)10.1063/1.1996845 (DOI)000230596000063 ()2-s2.0-24144441232 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
5. Integration of colossal magnetoresistors with GaAs
Open this publication in new window or tab >>Integration of colossal magnetoresistors with GaAs
2005 (English)In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 284, no 02-jan, 1-5 p.Article in journal (Refereed) Published
Abstract [en]

Colossal magnetoresistive (CMR) La0.67Ca0.33MnO3 (LCMO) and La0.67Sr0.33MnO3 (LSMO) films have been grown by pulsed laser deposition technique on GaAs(001) substrates buffered with epitaxial MgO layer. X-ray diffraction revealed strong c-axis out-of-plane orientation and strong in-plane texture of CMR/MgO bilayers on GaAs single crystal. The maximum temperature coefficient of resistivity TCR = 9.0% K-1 at 223 K and 2.0% K-1 at 327 K. and the magnetoresistance Delta rho/rho similar to-7.95% kOe(-1) and -1.47% kOe(-1) have been achieved for LCMO/MgO/GaAs and LSMO/MgO/GaAs heteroepitaxial structures, respectively. Comparison with the test LCMO and LSMO films grown directly onto the bulk MgO(001) single cry tal demonstrates the identity of LSMO/MgO/GaAs and LSMO/MgO films properties whereas the LCMO films grown on MgO buffered GaAs show lower transition temperature T-c = 242 K compared to 253 K in LCMO/MgO.

Keyword
PVD, manganites, colossal magnetoresistivity, uncooled infrared bolometers, mgo buffer layers, thin-films, epitaxial-growth
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-15086 (URN)10.1016/j.jcrysgro.2005.06.054 (DOI)000232387900001 ()2-s2.0-25144452481 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
6. The effect of strained Si1-xGex and Si1-yCy layers for La0.75Sr0.25MnO3 films grown on oxide-buffered Si substrates.
Open this publication in new window or tab >>The effect of strained Si1-xGex and Si1-yCy layers for La0.75Sr0.25MnO3 films grown on oxide-buffered Si substrates.
2006 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 99, no 1Article in journal (Refereed) Published
Abstract [en]

We report the effect of strain on the structural and electrical properties of colossal magnetoresistive (CMR) La0.75Sr0.25MnO3 (LSMO) films grown on Bi4Ti3O12/CeO2/ yttrium-stabilized-zirconia-buffered Si1-xGex/Si (x=0-0.20) and Si1-yCy/Si (y=0-0.01) substrates. The strain in the buffer layer stack was tailored by varying the Ge and C contents in SiGe and SiC layers. It has been demonstrated that the relaxation of Bi4Ti3O12 layer is dependent on Ge content and this strongly affects the quality of the LSMO film. The surface roughness of LSMO was also strain dependent and samples grown on SiGe and SiC template layers were significantly smoother than that on Si. High resistivity and low values of the temperature coefficient of resistivity were obtained in LSMO films on Si0.8Ge0.2/Si and Si0.99C0.01/Si whereas Si0.9Ge0.1/Si sample shows a slight improvement in the crystalline and electrical LSMO properties compared to the CMR film grown onto the Si substrate.

Keyword
thin-films, dielectric-properties, manganites
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-15374 (URN)10.1063/1.2150260 (DOI)000234607200072 ()2-s2.0-30844455355 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
7. Microfabrication of epitaxial La1-x(Sr,Ca)(x)MnO3 IR bolometer on Si
Open this publication in new window or tab >>Microfabrication of epitaxial La1-x(Sr,Ca)(x)MnO3 IR bolometer on Si
2006 (English)In: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 80, 47-54 p.Article in journal (Refereed) Published
Abstract [en]

Self supported free standing heteroepitaxial La1-x(Sr,Ca)(x)MnO3 (LSCMO) membranes grown on Bi4Ti3O12(BTO)/CeO2/YSZ buffered Si substrates have been microfabricated by Ar ion beam etching (IBE) and SF6/C4F8 inductively Coupled plasma (ICP) etching technique. The electrical property of free standing membrane was compared to as-grown sample by four point measurement. These results demonstrate feasibility to use heteroepitaxial oxide film structures with conventional photoresist patterning as thermally isolated membranes for infrared microbolometers.

Keyword
microfabrication, manganite, free stanching membrane, uncooled infrared bolometer, Ar ion beam etching, photoresist, films, silicon
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-15799 (URN)10.1080/10584580600656171 (DOI)000238680700007 ()2-s2.0-33745740848 (Scopus ID)
Note
QC 20100525, QC 20110929. Conference: 17th International Symposium on Integrated Ferroelectrics. Shanghai, PEOPLES R CHINA. APR 17-20, 2005 Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
8. Wet etching study of La-0.67(Sr0.5Ca0.5)(0.33)MnO3 films on silicon substrates
Open this publication in new window or tab >>Wet etching study of La-0.67(Sr0.5Ca0.5)(0.33)MnO3 films on silicon substrates
2008 (English)In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 37, no 3, 361-367 p.Article in journal (Refereed) Published
Abstract [en]

Wet etching of colossal magnetoresistive (CMR) perovskite La-0.67(Sr0.5Ca0.5)(0.33)MnO3 (LSCMO) films on Bi4Ti3O12/CeO2/yttrium-stabilized zirconia (YSZ)-buffered Si substrates was investigated using potassium hydroxide (KOH) and buffered hydrofluoric acid (BHF) solutions. X-ray diffraction (XRD) and scanning spreading resistance microscopy (SSRM) measurements revealed that the morphological roughness of the LSCMO films increases, while the electrical resistance roughness decreases, with increasing KOH etching time. The LSCMO films are highly chemically resistant to KOH solution; however, in the case of BHF etching, an etch rate of 22 nm/min was obtained with high selectivity over a photoresist mask.

Keyword
etch rate, manganite, selectivity, KOH, BHF, SSRM, spreading resistance microscopy, thin-films, infrared detectors, fabrication, manganite, carriers, nife
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-17275 (URN)10.1007/s11664-007-0343-x (DOI)000252483100016 ()2-s2.0-38349155865 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
9. Wet and dry etching of La-0.67(Sr,Ca)(0.33)MnO3 films on Si.
Open this publication in new window or tab >>Wet and dry etching of La-0.67(Sr,Ca)(0.33)MnO3 films on Si.
2006 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, no 2, 587-590 p.Article in journal (Refereed) Published
Abstract [en]

We report etching processes of epitaxial La-0.67(Sr,Ca)(0.33)MnO3 (LSCMO) colossal magnetoresistive (CMR) films grown on Bi4Ti3O12/CeO2/YSZ oxide-buffered Si using buffered HF (BHF), potassium hydroxide (KOH) and Ar ion beam etching (IBE) methods. LSCMO films demonstrate high resistivity against the KOH etchant whereas 22 nm/min etching rate was obtained in the BHF with high selectivity over photoresist and Si. Compared to 24 nm/min for Si, Ar IBE yields 16 nni/min etching rate for the LSCMO film and the oxide-buffer layers.

Keyword
colossal magnetoresistors, etching rate, Si, KOH, BHF, Ar ion beam, crystalline silicon, alkaline-solutions
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-16055 (URN)10.1016/j.tsf.2005.12.183 (DOI)000241220600049 ()2-s2.0-33748765526 (Scopus ID)
Note
QC 20100525 QC 20110928. Conference: 12th International Conference on Thin Films. BRATISLAVA, SLOVAKIA. SEP 15-20, 2002Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved

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