摘要:

The technology of high‐resolution focused ion beams has advanced dramatically in the past 15 years as focusing systems have evolved from laboratory instruments producing minuscule current densities to high current density tools which have sparked an important new process: direct micromachining at the micrometer level. This development has been due primarily to the exploitation of field emission ion sources and in particular the liquid‐metal ion source. Originally developed in the early 1960’s as a byproduct of the development of electrostatic rocket engines, the liquid‐metal ion source was adapted for focused beam work in the late 1970’s, when it was demonstrated that submicrometer focused ion beams could be produced with current densities greater than 1 A cm−2. Ions can be produced with liquid‐metal ion sources from elements including Al, As, Au, B, Be, Bi, Cs, Cu, Ga, Ge, Fe, In, Li, P, Pb, Pd, Si, Sn, and Zn. In the past decade, focused ion beam systems with liquid‐metal ion sources have had a significant impact on the semiconductor industry as they were applied to new and greatly improved methods of failure analysis, as well as circuit repair and modification,insituprocessing, and lithographic mask repair. This article discusses field emission ion sources, high‐resolution ion focusing systems, and means for analyzing their performance. A number of technologically interesting and useful applications are also discussed.

ISSN:0034-6748    

DOI:10.1063/1.1144104

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

An advanced configuration of minimum‐Bfield is designed for the electron cyclotron resonance (ECR) multicharged ion sources. The aim is to dramatically increase the efficiency of ion beam extraction by correcting the deformed magnetic flux tube containing hot plasma. The correction is performed by reversing the polarity of successive multipoles in the longitudinal direction. This method enables us to adopt the quadrupole that causes the greatest deformation. In addition, the most intense electron acceleration can be achieved with the quadrupole, since the radial field gradient is the largest of all multipoles.

ISSN:0034-6748    

DOI:10.1063/1.1144105

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The design and performance of a new‐type source of negative ions is presented. This device retains the idea of the so‐called reversal electron attachment detector [READ, M. T. Bernius and A. Chutjian, J. Appl. Phys.66, 2783 (1989)] to produce low‐energy electrons by reversing electron trajectories at an electrode. Electrons are produced in the present device by several ribbon filaments that surround a cylindrical wire grid. They are accelerated through the grid, then decelerated to zero, or near‐zero velocity at the surface of a tube. The tube (anode) is perforated with small holes through which effuse the target molecules. Electrons attach to form either parent and/or fragment negative ions. Attachment takes place at a location above the anode corresponding to a match between the electron energy and the attachment resonance energy. Negative ions are pulsed out of the attachment region and focused onto the entrance plane of a quadrupole mass selector. Electron and ion trajectory calculations are presented, and the performance illustrated with six molecules having attachment resonances in the range 0.0–2.2 eV. The detection sensitivity as measured using the method of standard additions is below 1 part‐per‐trillion, with a calculated conversion rate (ions/electrons) of 1.3%. Signal nonlinearity is discussed in terms of ion space‐charge effects. The device also produces positive ions, and an analogous treatment may be carried through to characterize its performance in this mode.

ISSN:0034-6748    

DOI:10.1063/1.1144106

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

An experimental method has been developed for the determination of ion multiplier sensitivity to ions of different mass to charge ratio using the electron‐ion coincidence technique of dipole (e,e+ion) spectroscopy. Time‐of‐flight mass spectra of each of the noble gas atoms He, Ne, Ar, Kr, and Xe are collected using the ion multiplier under investigation. In the present work we have determined relative efficiencies, at 7.5–8 keV ion impact energy, over the mass range 1–140 amu for two different large active area multipliers, a Johnston focused mesh multiplier and a microchannel‐plate detector, both operated in the saturated pulse counting mode. Significant variations in detector sensitivity occur at lowm/evalues for both multipliers. The microchannel‐plate detector shows a level response function abovem/e=∼30, while the Johnston multiplier exhibits a slow decrease in sensitivity in the same mass range. The applicability of the measured response functions to the correction of molecular mass spectra and experimental photoion branching ratio data has been investigated. It appears that the detection efficiencies for atomic and polyatomic ions of the samem/emay be different.

ISSN:0034-6748    

DOI:10.1063/1.1144107

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A small, compact negative‐ion source based on plasma sputtering has been developed for secondary‐ion mass spectrometry (SIMS). It can make precise measurements of the oxygen isotope ratios in minerals. From a copper sputter target, a high‐density63Cu−ion beam of 3 mA cm−2has been obtained as the primary‐ion beam with a size of 100 &mgr;m in diameter. The mass distribution of the ion beam is 99% Cu−and 1% Cu−2ions; other ionic species comprise less than 0.1%. A typical beam stability for 10 min has been achieved at 0.4% (&sgr;). These performances of the negative‐ion source are useful to performinsituanalyses of insulator materials in SIMS. As an application, the high‐mass resolution spectra for three isotopes of oxygen secondary ions from an insulator sample bombarded by the63Cu−ion beam was studied.

ISSN:0034-6748    

DOI:10.1063/1.1144108

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

An intense pulsed beam of CH3Cl in the ‖111≳ statewithoutvelocity selection was focused using a 2‐m electrostatic hexapole field. The beam intensity was estimated to be ∼1×1013molecules pulse−1, which is much greater than the similar beams in the earlier study of Gandhietal. by at least two orders of magnitude. The beam had a 3‐ms pulse width and was focused with an angular divergence of 0.7 mrad. The improvements in beam intensity and in the divergence of the beam can be mainly ascribable to the efficient pumping of the hexapole field through the cylindrical electrodes, which enables us to employ the helium seeding to have the fast stream velocity, the narrow distribution of velocity, and the aerodynamic effects. Those factors altogether made the velocity selection of the beam unnecessary.

ISSN:0034-6748    

DOI:10.1063/1.1144109

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A monostatic pulsed CO2Doppler lidar operating in a short‐pulse (<1 &mgr;s), high‐pulse‐repetition‐frequency (≳1 kHz), low‐pulse energy (1–10 mJ) mode has been developed for Doppler and return‐power measurements within the planetary boundary layer. The system has achieved near‐quantum‐limited performance, demonstrating a Doppler measurement capability to approximately 5 km with pulse energies of 1–2 mJ.

ISSN:0034-6748    

DOI:10.1063/1.1144110

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

In order to characterize fluorescent light, we present a decay time measurement method based on the use of a commercial photon counting module. This module, adapted for all fiber measurements, is well adapted for the developing field of optodes for chemical and biochemical sensing. Moreover, it improves the detection sensitivity to the femtowatt and picowatt range. It is thus possible to excite the fluorescence with very low power pump pulses, down to a few nanowatts, and to measure the temporal distribution of the fluorescent signal. As sources we can use LEDs, or white lamps plus a monochromator, avoiding unwanted phenomena such as saturation, amplified spontaneous emission (ASE), and excited state absorption (ESA). We obtain a measurement accuracy of 0.1% in a couple of minutes.

ISSN:0034-6748    

DOI:10.1063/1.1144111

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A new type of circular dichroism (CD) spectrometer has been designed and constructed based on a principle which is entirely different from that of commercial CD spectrometers. The Mueller matrix approach is used to analyze and evaluate important factors determining its performance, which is revealed to be dependent upon (1) the quality of a depolarizer, (2) the residual static birefringence inherent in a collimator lens, a photoelastic modulator, and an analyzer. Furthermore, the polarization characteristics of both a monochromator and a detector are found to have no effect on CD signal in the new CD spectrometer. Thus, a double‐grating monochromator can be used instead of a double‐prism monochromator. The total performance of the new CD spectrometer is ascertained to be equivalent to that of commercial CD instruments. With using a lock‐in amplifier tuned to 100 kHz, the new CD spectrometer can be easily converted into a linear dichroism spectrometer.

ISSN:0034-6748    

DOI:10.1063/1.1144112

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We present a new method to measureinsituthe amplitude of the retardation for a photoelastic modulator polarimeter using single photon counting techniques. The method allows the simultaneous measurement of linear and circular polarization of light without the need for a separate calibration procedure. Comparison with measurements made with a &lgr;/4‐retarder polarimeter show excellent agreement, confirming the method used.

ISSN:0034-6748    

DOI:10.1063/1.1144113

出版商:AIP    

年代:1993

数据来源: AIP