Brandon Van Leer

Nanoscale three-dimensional imaging of the human myocyte

The ventricular human myocyte is spatially organized for optimal ATP and Ca(2+) delivery to sarcomeric myosin and ionic pumps during every excitation-contraction cycle. Comprehension of three-dimensional geometry of the tightly packed ultrastructure has been derived from discontinuous two-dimensional images, but has never been precisely reconstructed or analyzed in human myocardium. Using a focused ion beam scanning electron microscope, we created nanoscale resolution serial images to quantify the three-dimensional ultrastructure of a human left ventricular myocyte. Transverse tubules (t-tubule), lipid droplets, A-bands, and mitochondria occupy 1.8, 1.9, 10.8, and 27.9% of the myocyte volume, respectively. The complex t-tubule system has a small tortuosity (1.04±0.01), and is composed of long transverse segments with diameters of 317±24nm and short branches. Our data indicates that lipid droplets located well beneath the sarcolemma are proximal to t-tubules, where 59% (13 of 22) of lipid droplet centroids are within 0.50μm of a t-tubule. This spatial association could have an important implication in the development and treatment of heart failure because it connects two independently known pathophysiological alterations, a substrate switch from fatty acids to glucose and t-tubular derangement.

Nanomechanical properties of piezoresistive cantilevers: Theory and experiment

Concise analytical expressions for the effective spring constant, resonance frequency, and effective mass are derived using elementary beam theory for cantilevers, which exhibit a basic rectangular cross section modified by a rectangular hole centered at the base, which is a typical case for piezoresistive cantilevers. The results demonstrate that each of these mechanical properties can be represented as the property of the same cantilever in the absence of the hole times a dimensionless function of the hole geometry. The derivations are used to determine the mass sensitivity of the modified levers and to optimize the mass sensitivity of the piezoresistive geometry. The beam theories are shown to be consistent with two dimensional plate theory (finite element analysis) and in good agreement with our experimental results on cantilevers milled using a focused ion beam.

Sideways FIB TEM sample preparation for improved construction analysis in TEM

Conventional TEM sample preparation for full-stack BEOL construction analysis (CA) has several issues such as the difficulty of achieving full metal layers intact in a single lamella, and also a curtaining effect that adversely impacts TEM analysis. This paper presents and successfully demonstrates an alternative sample preparation technique for preparing CA samples with full-BEOL metal stack. The procedure involves changing the orientation of the lamella by rotating the sample during in situ FIB attachment and milling it sideways to achieve lamella thickness of 100 nm, with uniform thickness at the area of interest. With this new method, full metal layers can be preserved while minimizing the curtaining effect often observed in heterogeneous TEM sample preparation.

Ga+ and Xe+ FIB Milling and Measurement of FIB Damage in Aluminum

S/TEM sample preparation of aluminium and aluminium alloys to characterize grain boundary phases by focused ion beam (FIB) continues to be a major interest in metallurgical analysis because of FIB’s ability to prepare site specific specimens and eliminating damage from mechanical polishing or electro-polishing [1]. Recent instrumentation using plasma FIB (PFIB) technology and Xe ions offer increased milling rates because of its ability to deliver 30 – 40 times more current compared to Ga FIBs. While the measured sputter rate of aluminum using Ga and Xe differs by about 25% (0.31 m/nC [Ga] and 0.41 m/nC [Xe]), the ability to use more current for micromachining will allow users to increase throughput significantly and prepare much larger cross-sections for S/TEM sample preparation if PFIB is employed. Therefore, it is of interest to understand the amount of FIB damage introduced into the sidewall of a thin section of aluminum by FIB. 30 kV FIB damage employing a different preparation method has been measured to be ~ 4 nm [2].

Xe+ FIB Milling and Measurement of Amorphous Damage in Diamond

Microand nanomachining of diamond using focused ion beam (FIB) continues to generate interest in applications such as diamond anvil cells, photonic devices, micro-cantilevers and tools for imprinting applications [1,2]. However, the milling rate of diamond by FIB is approximate 4X slower when compared to silicon using 30 kV Ga FIB [3]. Recent instrumentation using PFIB technology and Xe ions offer increased milling rates because of their ability to deliver up to 30X more current compared to Ga FIBs. While the sputter rate of diamond using Ga and Xe differs only slightly (0.07 μm/nC [Ga] and 0.09 μm/nC [Xe]), the ability to use more current for micromachining will allow users to increase throughput significantly. Therefore, it is of interest to understand the amount of amorphous damage introduced into a sidewall of diamond. Previous results indicate that for a glancing angle ~0 degrees, up to 35 nm of amorphous damage is introduced by Ga FIB in single crystal diamond [4].

Ga + FIB Milling and Measurement of FIB Damage in Sapphire

Single crystal Al2O3 (sapphire) is an important material for LED, optical and RFIC manufacturing because of its durability, thermal insulation, chemical inertness and light transmission [1]. Site-specific S/TEM sample preparation for LED specimens require the use of a FIB or DualBeam to characterize active areas for defects and process characterization. Minimizing surface damage during FIB specimen preparation is an important factor for high quality analytical results, especially in the case of TEM lamella. It has been shown in previous experimental studies that the milling process of high energy Ga +

Focused Ion and Electron Beam Techniques

This chapter gives a brief detail on the focused ion and electron beam techniques. A DualBeam is a focused ion beam (FIB) column and a scanning electron microscope (SEM) on the same platform. Commercial FIB columns generally use Ga ions and are available with energy ranges from 500 eV to 30 keV. Commercial SEM columns are available with energy ranges from 200 eV to 30 keV, with beam currents up to 200 nA, with an ultimate resolution of 0.9 nm. The FIB or SEM can be directly used for fabrication of MEMS/ NEMS structures. The electron or ion beam energy and spot size may be varied to yield different milling or deposition characteristics. DualBeam techniques may be utilized to either directly fabricate MEMS/NEMS devices or to site specifically section and image MEMS/NEMS devices. FIB milling can be used to site specifically remove material to create MEMS/NEMS devices. The FIB can also be used to site specifically deposit structures either in the plane or out of the plane of the substrate. The deposit height varies where different bitmap grayscale values define unique dwell times of the beam. The SEM can also be used for electron beam lithography applications using metallization and lift-off techniques. The microscopic optical semiconductor mirror device that is the backbone of the Texas Instruments DLP projection systems is a well-known commercially available MEMS structure. DualBeam can be used to directly prototype or manufacture MEMS devices, as well as characterize the devices made by the DualBeam or by some other process.