Lucille A. Giannuzzi

FIB Lift-Out Specimen Preparation Techniques

In this chapter, we review methods and applications of the FIB lift-out specimen preparation technique. A historical overview of the development of the technique is given. The ex-situ and in-situ lift-out techniques are described. Examples, advantages, and disadvantages of each of the techniques are presented.

Electron-beam induced recrystallization in amorphous apatite

Electron-beam induced recrystallization of irradiation-induced amorphous Sr2Nd8(SiO4)6O2 is investigated in situ using transmission electron microscopy with 200keV electrons at room temperature. Epitaxial recrystallization is observed from both the amorphous/crystalline interface and the surface, and the recrystallization is more pronounced with increasing electron-beam flux. Since the temperature increase induced by electron-beam irradiation is estimated to be less than 7K and maximum energies transferred to target atoms are below the displacement energies, ionization-induced processes are considered to be the primary mechanisms for the solid-phase epitaxial recrystallization observed in the present study.

Ion - Solid Interactions

In this chapter we summarize reactions that take place when an energetic ion impinges on a target surface. The results based on equations that are usually used to estimate ion range and ion sputtering in amorphous materials are presented. A discussion on ion channeling and ion damage in crystalline materials is presented. The problems of redeposition associated with an increase in sputtering yield within a confined trench are presented. Knowledge of ion - solid interactions may be used to prepare excellent quality FIB milled surfaces.

Replacing a failed mini-implant with a miniplate to prevent interruption during orthodontic treatment

INTRODUCTIONnWhen mini-implants fail during orthodontic treatment, there is a need to have a backup plan to either replace the failed implant in the adjacent interradicular area or wait for the bone to heal before replacing the mini-implant. We propose a novel way to overcome this problem by replacement with a miniplate so as not to interrupt treatment or prolong treatment time.nnnMETHODSnThe indications, advantages, efficacy, and procedures for switching from a mini-implant to a miniplate are discussed. Two patients who required replacement of failed mini-implants are presented. In the first patient, because of the proximity of the buccal vestibule to the mini-implant, it was decided to replace the failed mini-implant by an I-shaped C-tube miniplate. In the second patient, radiolucencies were found around the failed mini-implants, making the adjacent alveolar bone unavailable for immediate placement of another mini-implant. In addition, the maxillary sinus pneumatization was expanded deeply into the interradicular spaces; this further mandated an alternative placement site. One failed mini-implant was examined under a scanning electron microscope for bone attachment.nnnRESULTSnTreatment was completed in both patients after replacement with miniplates without interrupting the treatment mechanics or prolonging the treatments. Examination under the scanning electron microscope showed partial bone growth into the coating pores and titanium substrate interface even after thorough cleaning and sterilization.nnnCONCLUSIONSnReplacement with a miniplate is a viable solution for failed mini-implants during orthodontic treatment. The results from microscopic evaluation of the failed mini-implant suggest that stringent guidelines are needed for recycling used mini-implants.

Gallium-Induced Milling of Silicon: A Computational Investigation of Focused Ion Beams

Molecular dynamics simulations are performed to model milling via a focused ion beam ~FIB! .T he goal of this investigation is to examine the fundamental dynamics associated with the use of FIBs, as well as the phenomena that govern the early stages of trench formation during the milling process. Using a gallium beam to bombard a silicon surface, the extent of lateral damage ~atomic displacement! caused by the beam at incident energies of both 2 and 30 keV is examined. These simulations indicate that the lateral damage is several times larger than the beam itself and that the mechanism responsible for the formation of a V-shaped trench is due to both the removal of surface material, and the lateral and horizontal migration of subsurface silicon atoms toward the vacuum/crater interface. The results presented here provide complementary information to experimental images of trenches created during milling with FIBs.

Computed Tomographic Spectral Imaging: 3D STEM-EDS Spectral Imaging

Spectral imaging, where complete x-ray spectra are acquired from 2D or 3D arrays of points, is a powerful microanalytical technique, especially when combined with multivariate statistical analysis [1]. Chemical imaging, typically spectroscopic imaging or mapping with energy-loss electrons or x rays has been performed on flat [2-3] or pillar-shaped specimens [4] in the TEM to achieve 3D chemical images. In this paper we describe results from acquisition and analysis, via multivariate statistical analysis (MSA), of x-ray spectral images acquired from a needle-shaped FIB specimen, tilted from -90 to +90 in a newly available TEM specimen holder from Fischione Instruments [5], with full EDS coverage and constant thickness throughout the tomographic series.

Molecular dynamics simulations of 30 and 2 keV Ga in Si

Focused Ga+ ion beams are routinely used at high incident angles for specimen preparation. Molecular dynamics simulations of 2 and 30keV Ga bombardment of Si(011) at a grazing angle of 88° were conducted to assess sputtering characteristics and damage depth. The bombardment of atomically flat surfaces and surfaces with vacancies shows little energy transfer yielding ion reflection. The bombardment of surfaces with adatoms allows for the coupling of the energy of motion parallel to the surface into the substrate resulting in sputtering. The adatom and one other Si atom eject, and motion in the substrate occurs down to a depth of 13A. Experimental evidence shows that sputtering is a reality, suggesting that an atomically flat surface is never achieved.

Recent Advances in FIB Technology for Nano-prototyping and Nano-characterisation

Combined focused ion beam (FIB) and scanning electron microscopy (SEM) methods are becoming increasingly important for nano-materials applications as we continue to develop ways to exploit the complex interplay between primary ion and electron beams and the substrate, in addition to the various subtle relationships with gaseous intermediaries. We demonstrate some of the recent progress that has been made concerning FIB SEM processing of both conductive and insulating materials for state-of-the-art nanofabrication and prototyping and superior-quality specimen preparation for ultra-high resolution scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM) imaging and related in situ nanoanalysis techniques.

Evidence for a Critical Amorphization Thickness Limit of Ga+ Ion Bombardment in Si

Focused ion beam (FIB) instruments which provide low energy (e.g., 2 keV) Ga ions offer a direct method for reducing conventional high energy (e.g., 30 keV) ion implantation damage for transmission electron microscopy (TEM) specimens [1], atom probe specimen preparation [2], and improvements in electron backscattered diffraction pattern quality [3]. As the ion energy is reduced, the ion range, and therefore the target surface damage, is also reduced [1]. However, there is a theoretical limit to the possible energy that can be used since the sputter yield (Y) also decreases as the ion energy decreases and a value Y less than 1 atom/ion implies that deposition of Ga rather than sputtering may occur. In this paper, we compare Ga ion implantation results into Si, Ta, and Au, from a FIB column operating at 2 keV and below.

Particle-induced x-ray emission in stainless steel using 30keV Ga+ focused ion beams

Characteristic x-ray emission from a well grounded stainless steel specimen using standard 30keV Ga+ focused ion beam instrumentation is demonstrated. X-ray yields are found to be on the order of 10−10 per incident ion, consistent with previous studies of low energy, high mass ion-solid interactions. X-ray yields were found to be highest for low energy transitions or low atomic number target atoms. Bremsstrahlung x-ray emission was found to be minimal, possibly increasing detectability compared with electron beam induced x-rays. Yields were also estimated to be on the order of 10−11 per sputtered atom, or approximately one x-ray per sputtered monolayer. While velocity coupling between the primary ion beam and target atom electrons is not possible under these experimental conditions, it is argued that x-ray emission is, in fact, due to recoil effects of the ion-solid interaction.