Charging of single Si nanocrystals by atomic force microscopy

Boer, E. A.; Bell, L. D.; Brongersma, Mark L.; Atwater, Harry A.; Ostraat, Michele L.; Flagan, Richard C.

doi:10.1063/1.1371783

Cited by 54 publications

(46 citation statements)

References 15 publications

(14 reference statements)

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“…The tapping mode experiments 9 involved samples of isolated Si nanocrystals made by an aerosol method and deposited on a 100 nm thermally grown SiO 2 layer on a Si substrate. In this case, the AFM tip was used to inject charge into isolated single nanoparticles that were subsequently imaged in the tapping mode.…”

Section: Methodsmentioning

confidence: 99%

“…Briefly, the noncontact mode experiments 8 involved Si nanocrystal samples consisting of 100 nm silicon dioxide layers ͑wet thermally grown on Si substrates͒ that were implanted at room temperature with 35 keV Si ϩ ions to a fluence of 4ϫ10 16 Si/cm 2 . The samples were annealed at 1100°C for 10 min in vacuum ͑base pressure Ͻ8ϫ10 Ϫ7 Torr͒ to allow the nucleation and growth of silicon nanocrystals ͑size ϳ2-6 nm͒.…”

Section: Methodsmentioning

confidence: 99%

“…͑1͒. Figure 2 shows an experimental line scan ͑solid line͒ of a charged region of an etched SiO 2 film containing silicon nanocrystals 8 superimposed on a calculated AFM scan ͑dot-ted line͒, determined using the model described in Sec. IV A.…”

Section: ͑5͒mentioning

confidence: 99%

“…1͒ is a useful tool to detect small numbers of charges 2 as well as to inject charge into a localized region. [3][4][5][6][7][8][9] However, quantitative measurement of electrostatic charge has never been straightforward because of the complex factors involved, such as tip shape, tip-sample distances, contamination or oxidation of tip and sample, and the exact nature of the tip-sample interaction. Models, varying in complexity from a parallel-plate capacitor to finiteelement calculations, are always needed to interpret results quantitatively.…”

Section: Introductionmentioning

confidence: 99%

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Models for quantitative charge imaging by atomic force microscopy

Boer

Bell

Brongersma

et al. 2001

Journal of Applied Physics

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Two models are presented for quantitative charge imaging with an atomic-force microscope. The first is appropriate for noncontact mode and the second for intermittent contact ͑tapping͒ mode imaging. Different forms for the contact force are used to demonstrate that quantitative charge imaging is possible without precise knowledge of the contact interaction. From the models, estimates of the best charge sensitivity of an unbiased standard atomic-force microscope cantilever are found to be on the order of a few electrons.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: ͑5͒mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Models for quantitative charge imaging by atomic force microscopy

Boer

Bell

Brongersma

et al. 2001

Journal of Applied Physics

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“…In this direction, conductive atomic force microscopy 6-8 ͑C-AFM͒ has been recently used to estimate from topographical images the amount of charge stored in Si-nc deposited on different substrates. 9,10 However, few works have been devoted to investigate the electrical properties of MOS-based memory devices with embedded Si-nc at the nanoscale. In this work, a C-AFM has been used to study the conduction mechanisms of SiO 2 gate oxides with Si-nc as storage nodes.…”

mentioning

confidence: 99%

Conduction mechanisms and charge storage in Si-nanocrystals metal-oxide-semiconductor memory devices studied with conducting atomic force microscopy

Porti

Avidano

Nafrı́a

et al. 2005

Journal of Applied Physics

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In this work, we demonstrate that conductive atomic force microscopy ͑C-AFM͒ is a very powerful tool to investigate, at the nanoscale, metal-oxide-semiconductor structures with silicon nanocrystals ͑Si-nc͒ embedded in the gate oxide as memory devices. The high lateral resolution of this technique allows us to study extremely small areas ͑ϳ300 nm 2 ͒ and, therefore, the electrical properties of a reduced number of Si-nc. C-AFM experiments have demonstrated that Si-nc enhance the gate oxide electrical conduction due to trap-assisted tunneling. On the other hand, Si-nc can act as trapping centers. The amount of charge stored in Si-nc has been estimated through the change induced in the barrier height measured from the I-V characteristics. The results show that only ϳ20% of the Si-nc are charged, demonstrating that the electrical behavior at the nanoscale is consistent with the macroscopic characterization. Memory devices based on metal-oxide-semiconductor ͑MOS͒ structures with Si nanocrystals ͑Si-nc͒ embedded in the gate oxide 1-5 show many advantages compared to the current floating gate technologies. In particular, they offer fast writing speeds at smaller injection voltages, extremely small degradation, smaller lateral leakage currents, and, therefore, longer retention times. These developments in nanoscale silicon electronics, however, require tools to locally characterize the electrical properties of the Si-nc. In this direction, conductive atomic force microscopy 6-8 ͑C-AFM͒ has been recently used to estimate from topographical images the amount of charge stored in Si-nc deposited on different substrates. 9,10 However, few works have been devoted to investigate the electrical properties of MOS-based memory devices with embedded Si-nc at the nanoscale. In this work, a C-AFM has been used to study the conduction mechanisms of SiO 2 gate oxides with Si-nc as storage nodes. The amount of charge stored in few Si-nc has also been estimated from electrical measurements.MOS structures with a SiO 2 thickness, t ox , of 23 nm ͓ob-tained from transmission electron microscopy ͑TEM͒ images͔ thermally grown on a p-type Si substrate and with a polysilicon gate have been analyzed. In some of them, the gate oxide was implanted with 15-keV Si + ions with a dose of 2 ϫ 10 16 cm −2 . 2 The peak concentration was estimated by simulation to be of about 10 at. % at a depth of ϳ22 nm with a width at half maximum of the ion implantation distribution within the oxide of ϳ9 nm. The rest were used as a measurement reference. After removing the polysilicon gate, 8 when working on bare oxides, the conductive tip of the C-AFM plays the role of the gate electrode. Therefore, MOS structures of only ϳ300 nm 2 can be analyzed. 8 The gate oxides ͑with and without Si-nc͒ were electrically characterized by measuring current-voltage ͑I-V͒ characteristics, obtained when a ramped voltage test ͑RVS͒, which consists of a forward followed by a backward voltage ramp, is applied at a fixed location of the oxide.To begin with, the electrical conduction of...

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Silicon Nanocrystals: Size Matters

Heitmann

Müller

Zacharias³

et al. 2005

Advanced Materials

290

155

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This paper reviews new approaches to size‐controlled silicon‐nanocrystal synthesis. These approaches allow narrowing of the size distribution of the nanocrystals compared with those obtained by conventional synthesis processes such as ion implantation into SiO2 or phase separation of sub‐stoichiometric SiOx layers. This size control is realized by different approaches to introducing a superlattice‐like structure into the synthesis process, by velocity selection of silicon aerosols, or by the use of electron lithography and subsequent oxidation processes. Nanocrystals between 2 and 20 nm in size with a full width at half maximum of the size distribution of 1 nm can be synthesized and area densities above 1012 cm–2 can be achieved. The role of surface passivation is elucidated by comparing Si/SiO2 layers with superlattices of fully passivated silicon nanocrystals within a SiO2 matrix. The demands on silicon nanocrystals for various applications such as non‐volatile memories or light‐emitting devices are discussed for different size‐controlled nanocrystal synthesis approaches.

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Charging of single Si nanocrystals by atomic force microscopy

Cited by 54 publications

References 15 publications

Models for quantitative charge imaging by atomic force microscopy

Models for quantitative charge imaging by atomic force microscopy

Conduction mechanisms and charge storage in Si-nanocrystals metal-oxide-semiconductor memory devices studied with conducting atomic force microscopy

Silicon Nanocrystals: Size Matters

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