Abstract:Mechanical resonators realized on the nanoscale by now offer applications in mass sensing of bio-molecules with extraordinary sensitivity. The general idea is that perfect mechanical mass sensors should be of extremely small size to achieve zepto-or yocto-gram sensitivity in weighing single molecules similar to a classical scale. However, the small effective size and long response time for weighing biomolecules with a cantilever restricts their usefulness as a high-throughput method. Commercial mass spectromet… Show more
“…We deduce for pristine diamond nanomembranes a FE threshold voltage of 1170 V from the I-V curve (Fig. 2(a) blue curve) which is in good agreement with the literature 24 .Figure 2( a ) Measured current as a function of the applied voltage (I-V) for a pristine diamond membrane and after 3, 6, and 9 cycles of ZnO ALD coating. The data has been smoothen by a simple moving average (n = 10) to guide the eyes.…”
The emission of electrons from the surface of a material into vacuum depends strongly on the material’s work function, temperature, and the intensity of electric field. The combined effects of these give rise to a multitude of related phenomena, including Fowler-Nordheim tunneling and Schottky emission, which, in turn, enable several families of devices, ranging from vacuum tubes, to Schottky diodes, and thermionic energy converters. More recently, nanomembrane-based detectors have found applications in high-resolution mass spectrometry measurements in proteomics. Progress in all the aforementioned applications critically depends on discovering materials with effective low surface work functions. We show that a few atomic layer deposition (ALD) cycles of zinc oxide onto suspended diamond nanomembranes, strongly reduces the threshold voltage for the onset of electron field emission which is captured by resonant tunneling from the ZnO layer. Solving the Schroedinger equation, we obtain an electrical field- and thickness-dependent population of the lowest few subbands in the thin ZnO layer, which results in a minimum in the threshold voltage at a thickness of 1.08 nm being in agreement with the experimentally determined value. We conclude that resonant tunneling enables cost-effective ALD coatings that lower the effective work function and enhance field emission from the device.
“…We deduce for pristine diamond nanomembranes a FE threshold voltage of 1170 V from the I-V curve (Fig. 2(a) blue curve) which is in good agreement with the literature 24 .Figure 2( a ) Measured current as a function of the applied voltage (I-V) for a pristine diamond membrane and after 3, 6, and 9 cycles of ZnO ALD coating. The data has been smoothen by a simple moving average (n = 10) to guide the eyes.…”
The emission of electrons from the surface of a material into vacuum depends strongly on the material’s work function, temperature, and the intensity of electric field. The combined effects of these give rise to a multitude of related phenomena, including Fowler-Nordheim tunneling and Schottky emission, which, in turn, enable several families of devices, ranging from vacuum tubes, to Schottky diodes, and thermionic energy converters. More recently, nanomembrane-based detectors have found applications in high-resolution mass spectrometry measurements in proteomics. Progress in all the aforementioned applications critically depends on discovering materials with effective low surface work functions. We show that a few atomic layer deposition (ALD) cycles of zinc oxide onto suspended diamond nanomembranes, strongly reduces the threshold voltage for the onset of electron field emission which is captured by resonant tunneling from the ZnO layer. Solving the Schroedinger equation, we obtain an electrical field- and thickness-dependent population of the lowest few subbands in the thin ZnO layer, which results in a minimum in the threshold voltage at a thickness of 1.08 nm being in agreement with the experimentally determined value. We conclude that resonant tunneling enables cost-effective ALD coatings that lower the effective work function and enhance field emission from the device.
“…A drawback to the approach was the small active area as the nanomembranes were approximately 200‐times smaller than MCPs. Recently, Kim et al (2016) demonstrated improved sensitivity, mass resolving power, and faster response times with ultrananocrystalline nanomembranes fabricated using conventional semiconductor etching processes. Mass spectra for two test proteins, insulin and cytochrome c , are shown in Figure 18.…”
Time-of-flight mass spectrometry (TOFMS) is one of the simplest and most powerful approaches for mass spectrometry. Realization of the advantages inherent in TOFMS requires innovation in the theory and practice of the technique. Instrumental developments, in turn, create new capabilities that enable applications in chemical measurement. This review focuses on the recent advances in TOFMS instrumentation. New strategies for ion acceleration, multiplexed detection, miniaturized TOFMS instruments, approaches to extend the length of ion flight, and novel ion detection technologies are reviewed. Techniques that change the basic paradigm of TOFMS by measuring m/z based on ion flight distance are considered, as are applications at the frontiers of instrumental performance.
“…The resulting variations of the electron current, which is emitted from the nanomembrane by field emission and subsequently amplified by the MCP unit, are used to sense the arrival of incoming analyte ions. [17][18][19][20][21][22] In addition, the implementation of independent conversion dynodes in front of the actual MCP proved to be particularly suitable. The analyte ions hit the conversion dynode, resulting in the generation of smaller secondary ions.…”
The developed booster-microchannel plate (BMCP) detector for MALDI-TOF mass spectrometry generates a relative signal amplification of over 20 for ions with m/z in the range of about 50 000–75 000 in comparison to the conventional MCP detector.
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