WO1993006470A1 - Electron detector device for spectroscopic analyses of surfaces under x-ray excitation - Google Patents
Electron detector device for spectroscopic analyses of surfaces under x-ray excitation Download PDFInfo
- Publication number
- WO1993006470A1 WO1993006470A1 PCT/EP1991/001771 EP9101771W WO9306470A1 WO 1993006470 A1 WO1993006470 A1 WO 1993006470A1 EP 9101771 W EP9101771 W EP 9101771W WO 9306470 A1 WO9306470 A1 WO 9306470A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- diode
- sample
- detector
- conversion
- ray
- Prior art date
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
- G01T1/28—Measuring radiation intensity with secondary-emission detectors
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
- G01N23/227—Measuring photoelectric effect, e.g. photoelectron emission microscopy [PEEM]
- G01N23/2273—Measuring photoelectron spectrum, e.g. electron spectroscopy for chemical analysis [ESCA] or X-ray photoelectron spectroscopy [XPS]
Definitions
- This invention refers to an electron detector device optimized for structural surface analyses using X-ray excita ⁇ tion spectroscop .
- the device operated under vacuum condi ⁇ tions, comprises basically a large size silicon diode that can detect both the X-ray fluorescence photons and the conversion electron resulting from the irradiation of the sample by the incident X-ray photons.
- X-ray absorption fine structures (“XAFS" spectra, as referred to in the scientific literature) are classically measured by monitoring the intensity of the X- ray fluorescence photons, or the intensity of the conversion electrons as a function of the energy of the monochromatic exciting X-ray beam. This requires, however, some suitable, detector.
- the detector output signal associated with each energy data point is digitized and stored in a computer memo- ry.
- the whole XAFS spectrum (corresponding to a complete scan of the monochromator) is finally reconstructed and analyzed according to more or less standard procedures so as to recover the structural information.
- the secondary emissions are most often collected with- in a restricted solid angle along a detection axis rotated by about 90° with respect to the incident X-ray beam exciting the sample.
- Standard detectors will respond not only to the con ⁇ version electrons, but also to the X-ray fluorescence photons, and, even worse, to a "variable" background of X-ray photons directly scattered or diffracted by the sample.
- the primary aim of the invention is to eliminate any radiative contribution and thus to enhance the "near-surface sensitivity" of the structural information.
- Figure 1 shows a schematic top-view of a device cor ⁇ responding to the invention.
- Figure 2 presents a functional diagram of a photodiode used in the detection device shown in Figure 1.
- Figure 3 is a top view of the photodiode considered in Figure 2.
- Figure 4 reproduces typical experimental spectra re- corded with a device corresponding to the invention. These spectra contain all the desired near-surface structural infor ⁇ mation. In this particular experiment, the sample was bulk tungsten metal with an oxidized overlayer.
- the sample 1 is suspended from a sample holder (not shown) inside a vacuum tight sample chamber 2 which also incorporates the whole detector assembly.
- An electrostatic screen 3 made of preformed copper foils or metallic grids, is disposed all around the sample except in the direction of the detector.
- An entrance slit 4 is cut into this electrostatic screen in order to allow the incident X-ray beam to strike the surface of the absorbing sample 1.
- the plane of incidence of the exciting X-ray beam is set horizont ⁇ al in the proposed experimental arrangement: this is usually preferable in terms of polarization of the incident beam but, alternatively, it could be set vertical as well (with only minor mechanical modifications).
- the detection assembly itself is set always perpendi ⁇ cular to the plane of incidence of the exciting X-ray beam impinging on the sample at about 90° from the direction of the X-ray beam.
- the first element of the detector assembly is a microchannel plate 5 set vertically. It is held in a support frame 6 machined from a highly insulating material (e.g. tef ⁇ lon), which carries also a large size photodiode 9 which is a non-standard component described below with reference to Figu- res 2 and 3 and which is the heart of the detection system.
- the primary function of the microchannel plate (MCP) 5 is to pre-amplify the signal of the conversion electrons. It is operated at a very low difference of potential between the polarization terminals 7 and 8, i.e. about 500 eV which re- suits in a very modest gain ( ⁇ 1000) compared to the standard operation mode recommended by the channel plate manufacturers and corresponding to typical gains of 10 5 to 10 8 . Under such operating conditions, the MCP 5 presents an extremely linear amplification characteristic which is essential for the pre- sent application. A further amplification is obtained by acce ⁇ lerating the intensified electron beam leaving the MCP before these electrons reach the photodiode.
- Second scan Second scan
- MCP terminal 7 -1900V ⁇ U ⁇ 1500V
- MCP terminal 7 -1900V ⁇ U ⁇ 1500V
- MCP terminal 8 -1000 V
- MCP terminal 8 -1000V Si-diode front-face:.0 V Si-diode front-face: 0 V Si-diode back-face: ground Si-diode back-face: ground
- the distance between the sample 1 and the MCP 5 may be, for example, 60 mm; the distance between the MCP 5 and the Si-diode may be 5 mm.
- the radiative emission i.e. X-ray scattering + X-ray fluorescence
- the radiative emission is entirely absorbed but a quite significant amount of secondary electrons can still be generated inside the channels and be amplified to ⁇ gether with the conversion photoelectrons which are of direct interest for the required analyses.
- the measured XAFS spectrum recorded at the output of the Si-diodes is "pol- luted" and distorted by signatures which are due to the radia ⁇ tive emission and not relevant to the surface of the sample.
- Figure 4 reproduces' the characteristic FT spectrum, of the XAFS data measured during the first scan (dashed line) and the FT spectrum corresponding to the difference discussed above (continuous line): a detailed interpretation of these spectra would fall far beyond the scope of the present disclo ⁇ sure but it is clearly apparent that a strong signature asso ⁇ ciated with the metallic tungsten substrate. (i.e. the W...W interatomic distance) is missing in the difference spectrum which is left with the only contribution of the oxide over- layer.
- Figure 4 is thus a good illustration of the typical "contamination" of the structural information contained in the surface sensitive contribution of the ' conversion photoelec ⁇ trons by spectral features due to the bulk sample and result- ing from the unwanted X-ray fluorescence contribution.
- the "key component” which is the Si- diode. It is made of a high resistivity n-type silicon wafer (280 um thick; 53x53 mm 2 ). As summarized in Figure 2, the junction results from the creation of a ion implanted p * layer 11, the interface zone between the n-type substrate 10 and the p* layer 11 constituting the space charge region 12. The thick ⁇ ness of the p * layer 11 is about 1300A.
- the active area of the front face is not coated with a protective aluminium layer: there are only provided a narrow peripheral strip plus a few axial strips 14 projecting therefrom towards the center of the free surface (see Figure 3).
- the aluminium strips disposed as described above are required to collect the detected charges and allow electrical contacts to be taken using ultra-sonic wire bonding techniques.
- the whole back face can be protected with an aluminium coating. Connections can then be made from both faces with a low noise electrometer (not shown) used for ultra-low current measurements.
- the thickness of the p * layer 11 has to be minimized: this is because the charges created in this p* layer need to diffuse to reach the junction with some probability to recombine without inducing any current detected by the elec ⁇ trometer. No Si0 2 nor aluminium protective coatings are provi ⁇ ded. However, due to the absence of such an overall protective layer on top of the active area, special care must be taken during operation: this means that the diode has to be kept under vacuum (just as the MCP!) and that water condensation and adsorption on the cold front face is not tolerated.
- the absence of Si0 2 overlayer minimizes the risk of damaging the junction when intense beams of electrons strike the active area: this is because, as established over the recent years, fixed charges tend to accumulate in the oxide and generate strong electric fields destructing the junction. This consideration may lead to protect the passivated Si0 2 strip 134 with a special teflon frame not shown in Figures 1 and 2.
- the very thin overlayer of native oxide on top of the p * layer 11 does not induce any notable degradation of the diode characteristics, e.g. any spectacular increase of the "dark" current.
- the Si-diode It is strongly recommended to operate the Si-diode at low temperature, typically at 150 K, in order to reduce the dark current generated in the diode but also in order to in ⁇ crease the equivalent shunt resistor of the diode which has to be made as large as possible so as to minimize the noise due to the residual offset voltage of the J-FET used as input stage of the electrometer (not discussed in this document).
- the detector should preferably be operated under good vacuum.
- the components of the detector asembly are all bake- able under a good primary vacuum at 400 K.
- the detector is compatible with the conventional, ultrahigh vacuum (UHV) requirements. This is a serious advantage of the present devi ⁇ ce over many classical detectors which do not survive high temperatures involved during the baking operation of the sa p- le chamber/detector prior to use.
- V 0 - 2250 V _+ 300 V): in this con- figuration the conversion photoelectrons emitted by the sample are synchroneously accelerated and blocked depending on the value of V B and the ac component of the signal delivered by the Si-diode should be directly proportional to the surface sensi ⁇ tive contribution of the conversion photoelectrons. It is noteworthy that the operation of the device without the pre-intensifying MCP proved also to be quite pos ⁇ sible in cases where the signal is very large. This simplifi ⁇ cation may find useful applications when the experiment is coupled to very intense synchrotron radiation X-ray sources of the 3rd generation.
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- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- High Energy & Nuclear Physics (AREA)
- Molecular Biology (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Analysing Materials By The Use Of Radiation (AREA)
Abstract
Description
Claims
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/EP1991/001771 WO1993006470A1 (en) | 1991-09-17 | 1991-09-17 | Electron detector device for spectroscopic analyses of surfaces under x-ray excitation |
JP3514903A JPH06510115A (en) | 1991-09-17 | 1991-09-17 | Electron detection device for spectroscopic analysis of surfaces under X-ray excitation |
EP91916107A EP0604415A1 (en) | 1991-09-17 | 1991-09-17 | Electron detector device for spectroscopic analyses of surfaces under x-ray excitation |
CA 2118921 CA2118921A1 (en) | 1991-09-17 | 1991-09-17 | Electron detector device for spectroscopic analyses of surfaces under x-ray excitation |
IE260792A IE922607A1 (en) | 1991-09-17 | 1992-08-24 | Electron detector device for spectroscopic analyses of¹surfaces under x-ray excitation |
PT100869A PT100869A (en) | 1991-09-17 | 1992-09-16 | ELECTRO DETECTOR DEVICE FOR SPECTROSCOPIC ANALYZES OF X-RAY SURFACES |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/EP1991/001771 WO1993006470A1 (en) | 1991-09-17 | 1991-09-17 | Electron detector device for spectroscopic analyses of surfaces under x-ray excitation |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1993006470A1 true WO1993006470A1 (en) | 1993-04-01 |
Family
ID=8165610
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/EP1991/001771 WO1993006470A1 (en) | 1991-09-17 | 1991-09-17 | Electron detector device for spectroscopic analyses of surfaces under x-ray excitation |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP0604415A1 (en) |
JP (1) | JPH06510115A (en) |
CA (1) | CA2118921A1 (en) |
IE (1) | IE922607A1 (en) |
PT (1) | PT100869A (en) |
WO (1) | WO1993006470A1 (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0602982A1 (en) * | 1992-12-17 | 1994-06-22 | Intevac, Inc. | Focused electron-bombarded detector |
WO1997014061A1 (en) * | 1995-10-06 | 1997-04-17 | University Of Leicester | Detector and method for autoradiography |
WO2005024405A1 (en) * | 2003-09-09 | 2005-03-17 | Council For The Central Laboratory Of The Research Councils | Ionising particle analyser enabling for exemple the separation of the fluorescent yield (fy) and the total electron yield (tey) in exafs (extended x-ray absorption fine structure) measurements |
EP3689902A1 (en) | 2013-03-15 | 2020-08-05 | Dana Farber Cancer Institute, Inc. | Flavivirus neutralizing antibodies and methods of use thereof |
WO2023081471A1 (en) | 2021-11-05 | 2023-05-11 | Dana-Farber Cancer Institute, Inc. | Human broadly crossreactive influenza monoclonal antibodies and methods of use thereof |
-
1991
- 1991-09-17 JP JP3514903A patent/JPH06510115A/en active Pending
- 1991-09-17 WO PCT/EP1991/001771 patent/WO1993006470A1/en not_active Application Discontinuation
- 1991-09-17 CA CA 2118921 patent/CA2118921A1/en not_active Abandoned
- 1991-09-17 EP EP91916107A patent/EP0604415A1/en not_active Withdrawn
-
1992
- 1992-08-24 IE IE260792A patent/IE922607A1/en not_active IP Right Cessation
- 1992-09-16 PT PT100869A patent/PT100869A/en not_active Application Discontinuation
Non-Patent Citations (2)
Title |
---|
NUCLEAR INSTRUMENTS AND METHODS. vol. A281, no. 1, 20 August 1989, AMSTERDAM NL pages 128 - 132; H. YAMAMOTO ET AL.: 'LOW-ENERGY NUCLEAR RADIATION DETECTION WITH A SILICON PHOTODIODE' * |
PATENT ABSTRACTS OF JAPAN vol. 6, no. 15 (P-134)(1030) 12 August 1982 & JP,A,57 072 072 ( FUJITSI K.K. ) 6 May 1982 * |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0602982A1 (en) * | 1992-12-17 | 1994-06-22 | Intevac, Inc. | Focused electron-bombarded detector |
WO1997014061A1 (en) * | 1995-10-06 | 1997-04-17 | University Of Leicester | Detector and method for autoradiography |
WO2005024405A1 (en) * | 2003-09-09 | 2005-03-17 | Council For The Central Laboratory Of The Research Councils | Ionising particle analyser enabling for exemple the separation of the fluorescent yield (fy) and the total electron yield (tey) in exafs (extended x-ray absorption fine structure) measurements |
US7432501B2 (en) | 2003-09-09 | 2008-10-07 | Council For The Central Laboratory Of The Research Councils | Ionising particle analyser enabling for example the separation of the fluorescent yield (FY) and the total electron yield (TEY) in EXAPS (extended X-ray absorption fine structure) measurements |
EP3689902A1 (en) | 2013-03-15 | 2020-08-05 | Dana Farber Cancer Institute, Inc. | Flavivirus neutralizing antibodies and methods of use thereof |
WO2023081471A1 (en) | 2021-11-05 | 2023-05-11 | Dana-Farber Cancer Institute, Inc. | Human broadly crossreactive influenza monoclonal antibodies and methods of use thereof |
Also Published As
Publication number | Publication date |
---|---|
IE922607A1 (en) | 1993-03-24 |
PT100869A (en) | 1994-05-31 |
CA2118921A1 (en) | 1993-04-01 |
JPH06510115A (en) | 1994-11-10 |
EP0604415A1 (en) | 1994-07-06 |
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