摘要:

We have fabricated dual‐gate Si metal–oxide semiconductor field effect transistor devices in which the lower gate is slotted and the upper gate, separated by 45 nm of SiO2, is planar. By appropriate adjustment of the potentials on the two gates, the field lines from the upper gate are pinched, creating an inversion layer about one‐half the slot width. The resist patterning was done by x‐ray lithography, using a mask that combined crystallographic‐template/sidewall‐shadowing techniques with UV lithography. The slotted lower gate was produced by lift‐off. The metallization was a sandwich structure of Cr/W/Cr which permitted high‐temperature annealing. Very high mobilities, ∼15 000 cm2/V s at 4.2 K, were achieved as a result. The combination of high mobility and extremely narrow inversion channel (∼30 nm) yields very clear structure in the conductance as a function of gate voltage, which cannot be accounted for by either localization effects or universal conductance fluctuations. Although these oscillations may be related to one‐dimensional subband effects, the magnetic field independence of the oscillations is not understood. At very high (12 T) magnetic fields an anomalous magnetoresistance has been seen.

ISSN:1071-1023    

DOI:10.1116/1.584182

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

This paper describes a new phenomenon about the diffraction of the ballistic electron by a transverse grating in the semiconductor. As a theoretical result, the diffraction efficiency changes almost between one and zero owing to a slight change in the average potential energy of the grating. For the grating of a 19‐nm pitch in GaInAs, we can change the diffraction efficiency between 0.88 and 0.001 by 0.1 V in the grating layer voltage. Applying this phenomenon to control of the electron transport, a new type of transistor is described.

ISSN:1071-1023    

DOI:10.1116/1.584183

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Freestanding wires of submicrometer width and with lengths up to 40 μm have been fabricated from single‐crystal GaAs and Si for studies of quantum transport. Fabrication techniques are described, and the low‐temperature properties for semiconductors and metals such as AuPd are compared. Fabrication of three‐terminal freestanding GaAs metal–semiconductor field effect transistor structures is demonstrated.

ISSN:1071-1023    

DOI:10.1116/1.584184

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

We have fabricated narrow wires and small rings from GaAs/AlGaAs double heterostructures by using electron beam lithography and dry etching techniques. We describe the nature of universal conductance fluctuations in a single wire and the magnetoresistance oscillations with a period of‐h/ein a ring structure. It is experimentally shown that (i) from a single wire experiment, electrons with energies differing by the correlation energyEcorr, have quite different magnetoresistance patterns, and (ii) from a ring experiment, the large aspect ratio (diameter/width) is important to obtain well‐defined oscillations.

ISSN:1071-1023    

DOI:10.1116/1.584185

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

One‐ and zero‐dimensional electron systems confined in GaAs/GaAlAs have been fabricated. The starting material consisted of a modulation doped and a double barrier diode heterostructure grown by molecular‐beam epitaxy. Very high resolution electron beam lithography and reactive ion etching were used to pattern lines and dots with widths ranging from 100 to 400 nm. Two measurement techniques have been applied: capacitance measurements of density of states—a novel technique for observing quantum effects in these structures—and resonant tunneling measurements. We have observed oscillations in capacitance spectroscopy which reflect discrete energy levels associated with one‐ and zero‐dimensional electron systems. Preliminary tunneling measurements are presented.

ISSN:1071-1023    

DOI:10.1116/1.584186

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

The nanofabrication techniques which are used to create quantum dot diodes will be discussed. The device is a vertical resonant tunneling diode where the lateral dimensions are reduced to ∼1000 Å. Electron beam lithography is used to pattern a small self‐aligned metal dot top contact and etch mask. The semiconductor dot is a cylinder ∼1000 Å in diameter and on the order of 100 Å thick, with the vertical potential defined by the double‐barrier heterostructure and the lateral defined by the Fermi‐level pinning of the free surfaces. Discrete energy states due to the three‐dimensional confinement are observed and are spin degenerate only. Transport measurements through such a device will be presented.

ISSN:1071-1023    

DOI:10.1116/1.584188

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Localized growth of metal lines on Si wafers has been demonstrated using a focused Ga+beam to selectively enhance the nucleation site density during a thermal chemical vapor deposition process. Iron and aluminum lines with thicknesses up to 2 μm have been formed using ion line doses between 4×1010and 4×1012Ga+/cm. Thus, the sensitivity of this process can be several orders of magnitude greater than ion beam induced polymerization techniques performed at room temperature. Auger analysis indicated that the total impurity concentration deep within the metal lines was roughly 15%. No Ga was detected in the deposited films.

ISSN:1071-1023    

DOI:10.1116/1.584189

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Electron beam induced chemical vapor deposition of W and Si has been studied in a transmission electron microscope. WF6and SiH2Cl2were used as gas sources. Si and W clusters were initially formed. The W clusters, ∼3 nm in size, were β‐W crystal, while the Si clusters were amorphous. Deposition rates can be directly calculated, by using these techniques. For example, a 120‐kV electron beam at 100 A/cm2current density will deposit W at ∼5 nm/min at 5×10−7Torr, and Si at 2 nm/min at 5×10−5Torr. A W rod, 15 nm in diameter, has been deposited using a 3‐nm‐diam focused electron beam.

ISSN:1071-1023    

DOI:10.1116/1.584190

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

A novel method is described which can be used for both the electrochemical deposition of metals in polymer films and the etching of metals with very high resolution. These faradaic processes are controlled using a scanning electrochemical microscope (similar to the scanning tunneling microscope). Patterns of silver and gold deposited in Nafion and poly(4‐vinylpyridine), respectively, with a linewidth smaller than 0.5 μm, and high‐resolution etching patterns in copper are shown. Extensions of this methodology to depositions of other materials, the use of other conducting polymer films, and possible applications for submicron devices are discussed.

ISSN:1071-1023    

DOI:10.1116/1.584191

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

In this preliminary study we have used a modified scanning tunneling microscope (STM) to directly deposit metallic features as small as 10 nm by decomposing organometallic gases containing tungsten and gold. Dots as well as lines have been formed. Tungsen deposits analyzed by Auger electron spectroscopy contained 48% tungsten, 40% carbon, and 12% oxygen. A resistivity of 0.01 Ω/cm for the deposits was measured by aligning the STM to a metal contact pattern. This is the first reported combination of STM lithography with conventional lithography. A discussion of several interesting physical and chemical mechanisms involved in the deposition process is also presented.

ISSN:1071-1023    

DOI:10.1116/1.584192

出版商:American Vacuum Society    

年代:1988

数据来源: AIP