The simulated ultrafast temporal response of the Au plasmonic bullseye lens studied in Fig. E r , inc is the maximum lateral electric field of the incident pulse and E z , center is the normal electric field at the bullseye center. The electric field is normalized to the maximum E r , inc. The enhancement, i. Enhancement is obtained by dividing the Fourier transform of E z , center by that of E r , inc.
The peak J 4 is plotted relative to the value of J 4 under cw illumination. The tops of both y axes correspond to the value under cw illumination. The simulated ultrafast temporal response of bullseye lenses with varying numbers of rings, N. The simulated ultrafast temporal response of bullseye lenses with varying groove depth, d. The simulated ultrafast temporal response of bullseye lenses with varying groove width, w.
Bullseye lenses fabricated using two methods. Cathodoluminescence CL spectromicroscopy of the plasmonic resonance. The electron-induced multicolor luminescence from a tilted lens is collected by a parabolic mirror and focused by a lens into a spectrometer.
The electron beam is scanned and a full CL spectrum is collected at each beam position. The spectra are fitted with a parabolic background plus a Lorentzian over a 0. The points indicate data over the fitting window after the background is subtracted, while the lines indicate the Lorentzian peak-shape fit to the data. Angle-resolved cathodoluminescence CL with e-beam at the structure center. The parabolic mirror is imaged through a band-pass BP filter centered at nm wavelength with nm bandwidth.
Far-field plots are then generated by transforming mirror coordinates to angular coordinates. The gray dashed lines trace the electron-beam entry hole and the open face of the parabolic mirror. The FDTD-simulated b and experimentally measured c CL far-field polar maps for the electron beam positioned at the center.
Angle-resolved cathodoluminescence CL for a four-ring lens when the electron beam is positioned off center. The dashed circles indicate the edges of the first groove. Learn about our response to COVID , including freely available research and expanded remote access support.
In operation, any one of a number of columns 10, each designed for a different application can be used with the SEM system This represents considerable savings in cost and space over prior art systems, each of which was designed for a particular narrow range of operation. In application, the system 12 will allow, for example, a facility of small means to significantly expand their range of research.
An alternate design includes an integrated column 10 and electron gun 16 assembly which is replaced as a unit. In some cases, this is beneficial, allowing the use of optimized gun-column combinations.
A further application and benefit of the system 12 is that it allows substitution of the specimen chamber in order to accommodate different size specimens, and substitution of the electron gun. The relatively small, light weight and uncomplicated detachable column makes this flexibility possible. Prior art columns are much more bulky and complicated due to their reliance on electromagnets, which add further bulk and complication to the system due to water cooling requirements.
The column 40 of FIG. The method of attachment shown is with flanges 46, 48 and bolts 50, but other methods of attachment are also included in the spirit of the invention. It is also well understood by those skilled in the art how to vacuum seal the various fittings and part interconnections, for example by use of O-rings, etc.
According to the present invention, any of the SEM parts 14, 16, 40, 42, 44 or combinations of them can be replaced as required for a particular measurement.
Dashed outline 44' symbolically represents replacing the lower portion 44 of the column. It is a cross sectional view taken along the center line of either of the cylindrical columns 10 or For clarity in illustrating, various details that will be understood by those skilled in the art are omitted, such as the flanges 18, 20, 46, 48, electrical connectors, vacuum details, etc. A variety of methods of providing these details will be apparent to those skilled in the art and need not be described in detail.
The electron gun 16 and chamber 14 are also shown without details, the design of these being fairly standard, except for the detachable feature.
Of course, both lenses 52 and 54 are also included in the column 10 of FIG. The condenser lens 52 provides demagnification of the electron beam. The main field strength is provided by two cylindrical shaped permanent magnets 56, All of the parts making up the magnetic circuit are cylindrical in structure. The condenser lens has an outer magnet structure 55 including permanent magnets 56 and 58 in contact with cap pieces 60 and 62 and center cylinder Caps 60 and 62 have holes 76, 78 for passage of an electron beam from gun A pole piece cylinder 66 is suspended within the structure 55, and has a cylindrical bore 67 therethrough positioned in line with holes 76, 78 for passing the electron beam.
The cylinder 66 is positioned relative to the caps 60, 62 to form first and second magnet gaps 80 and 82 in which a magnetic field exists for the purpose of condensing the electron beam. Two cylindrical coils 72 and 74 are positioned around the cylinder Saturation of the iron in caps 60, 62, center cylinder 64 and pole piece cylinder 66 is avoided by designing an adequate width i. The dimensions of the structure of FIG.
For example, the overall diameter D is 80 mm and the height H of the condenser lens is 53 mm. The separate pole piece cylinder 66 provides two gaps 80 and 82, forming two condenser lenses. The placement of the magnets 56, 58 in the outer portion of the magnetic circuit, away from the gaps 80, 82 is an important feature. It was found that stray fields on the optic axis 84 are reduced by positioning the permanent magnets far from the optic axis The tuning coils 72, 74 are placed around the cylinder 66, and between the cylinder 66 and the magnets 56, This positioning makes conservative use of space in the design as shown in FIG.
Another useful feature of the condenser lens design is the provision of an adjustable bypass of the permanent magnets 56, The bypass circuit includes cylindrical extensions 92 and 94 surrounding the magnets 56 and 58, The circuit also shows slip rings 68 and 70, positioned between the magnets 56, 58 and the extensions 92 and The magnetic slip rings 68, 70 can be adjusted from position 86 to position 88 indicated by dashed outline.
The positioning of the slip rings 68 and 70 provides additional adjustment to the magnetic field and corresponding demagnification of the lens. The lens coils 72 and 74 work in combination with the slip rings 68 and When the slip rings are in position 88, they complete a magnetic circuit bypassing the magnets 56, 58 and thereby minimize the magnetic field in the gaps. The use of set screws 90 and various other methods of securing the rings 68, 70 in position will be apparent to those skilled in the art.
To summarize the condenser lens, the novel combination includes permanent magnets for primary field production placed in the outer magnetic return path, a pole piece cylinder with preferably two gaps, tuning coils placed between the pole piece cylinder and outer return path, and an adjustable bypass circuit for variably bypassing the permanent magnets.
The objective lens 54 includes a tapered objective lens pole piece structure 95 including a cylinder 96 having a bore 98 therethrough for passage of an electron beam. The outer diameter tapers as it approaches the specimen The magnetic field extending from the end returns by way of a tapered, cylindrical return path The pole piece cylinder 96 extends further towards the specimen 94 than does the return path The resulting complete pole piece structure 95 including the end portion of cylinder 96 and portion , is of conical shape, having a minimum diameter closest to the specimen This structure 95 allows space for the specimen to be tilted while retaining the required close proximity of the specimen to the end As with the condenser lens 52, the objective lens 54 is also designed to generate the magnetic field primarily through use of a permanent magnet or magnets, which are positioned as far away from the pole piece as is practical.
A top portion of the lens 54 is integrally connected to the pole piece cylinder 96, and makes contact with the permanent magnet The bore 98 through the cylinder 96 opens into an enlargened bore or cavity in the top portion The cavity encloses a detector , such as a microchannel plate detector, upon which is mounted a pre-deflector coil The cavity also houses a final aperture which is positioned by way of extension The lens coil of the objective lens 54 is used for adjusting the focus of the beam on the specimen Focusing can also be achieved by varying the specimen 94 height, i.
The position of the elements 54, 52, 16 in FIG. Protrusions from the objective lens 54 and protrusions from the chamber 14 symbolically represent apparatus for sealably joining the column to the chamber. When the lens 54 is lowered into position on the chamber, the distance between the end of the conical pole piece structure 96 and the specimen is typically about 2 mm.
This close proximity places the specimen within the magnetic field of the objective lens TWIB zh. WOA1 zh. Particle-beam control electromagnet and irradiation treatment apparatus equipped therewith. USB2 en. Permanent-magnet particle beam apparatus and method incorporating a non-magnetic metal portion for tunability. JPY2 ja. EPB1 en. USB1 en. Swinging objective retarding immersion lens electron optics focusing, deflection and signal collection system and method.
JPB2 ja.
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