Effectively controlling quantum mechanical tunneling through an ultrathin dielectric represents a fundamental materials challenge in the quest for high-performance metal-insulatormetal (MIM) diodes. Such diodes are the basis for alternative approaches to conventional thin-fi lm transistor technologies for large-area information displays, [ 1 , 2 ] various types of hot electron transistors, [2][3][4][5][6] ultrahigh speed discrete or antennacoupled detectors, [7][8][9][10][11][12][13][14] and optical rectennas. [ 15 ] MIM diodes have been fabricated by anodization, [ 1 ] thermal oxidation, [ 8-11 , 14 ] plasma oxidation, [ 10 , 12 , 13 ] or plasma nitridation [ 16 ] of crystalline metal fi lms. Diodes fabricated using these approaches have invariably exhibited poor yield and performance. These problems are to a large extent a consequence of the roughness of the surface of the crystalline metal fi lm, which is often larger than the thickness of the MIM insulator. As a result, the electric fi eld across a MIM device will be highly nonuniform, making the control of quantum mechanical tunneling problematic. In this contribution, we describe the use of an amorphous metal contact as a critical component for circumventing the surface roughness and fi eld uniformity roadblocks that have precluded the realization and utility of MIM electronics for applications requiring high device current rectifi cation ratios (e.g. display applications).The MIM diode is the fundamental building block of metalinsulator electronics. The device is characterized by a high degree of nonlinearity in its current-voltage characteristics as a result of a large difference in conductivity between on and off states. The operational theory of this diode, based on Fowler-Nordheim tunneling, has been described in detail by Simmons. [ 17 , 18 ] The probability of quantum mechanical tunneling depends exponentially on the thickness of the insulator between a pair of metal electrodes. Hence, the performance of the diode is critically dependent on the thickness uniformity of the tunnel-dielectric layer across the entire device. Interfacial roughness and dielectric imperfections give rise to alternate conduction mechanisms, e.g. Frenkel Poole emission, that can dominate at low voltages and reduce the device rectifi cation ratio. The inability to create and effectively control a uniform electric fi eld across the whole device area has been the primary limitation in producing reliable MIM devices. Here, we demonstrate that the necessary fi eld control can readily be achieved by integrating the atomically smooth-surface of an amorphous metal electrode with high-quality insulators. This combination provides a rich materials and processing palette for development of MIM electronics, enabling new strategies for device design and fabrication.Amorphous metals have been primarily investigated as bulk materials, addressing diverse applications that range from micromachines and hinges for digital light processors to golf clubs and transformer cores. [19][20][21] T...

Metal-insulator-metal (MIM) tunnel diodes on a variety of high and low work function metals with various levels of root-mean-square roughness are fabricated using high quality atomic layer deposited Al 2 O 3 as the insulating tunnel barrier. It is found that electrode surface roughness can dominate the current versus voltage characteristics of MIM diodes, even overwhelming the impact of metal work function. Devices with smoother bottom electrodes are found to produce current versus voltage behavior with higher asymmetry and better agreement with Fowler-Nordheim tunneling theory, as well as a greater percentage of functioning devices. V

A method is developed to estimate barrier heights of an asymmetric metal-insulator-metal (MIM) diode exhibiting Fowler-Nordheim tunneling. The method requires determination of slopes and intercepts of a log j I ðVþD/Þ 2 j versus 1 VþD/ plot rather than a log j I ðVÞ 2 j versus 1 V plot (i.e., a conventional Fowler-Nordheim plot), where I, V, and D/ refer to tunneling current, applied voltage, and the difference in barrier heights, respectively. As the value of D/ directly impacts the applied electric field magnitude, it is a critical component in barrier height determination from a current-voltage measurement. Conventional Fowler-Nordheim plot analysis does not employ D/, which compromises the accuracy of barrier height estimation when D/ 6 ¼ 0. Using the described method, the barrier heights of a ZrCuNiAl/Al 2 O 3 /Al MIM diode are estimated to be 1.75 V and 1.07 V, respectively, and the Al 2 O 3 tunneling effective mass is estimated to be 0.47. Additional MIM diodes are analyzed to show that the accuracy of MIM diode barrier height and effective mass estimates is highly sensitive to contamination and/or energy imparted during the deposition of the upper electrode. V

Bilayers of sputtered amorphous multicomponent metal films (AMMFs) and solution deposited amorphous oxide films have been reproducibly deposited with varying thicknesses of 20, 25, and 30 nm to form ordered nanolaminates. Interdiffusion is observed at the AMMF-oxide boundary, leading to unique interface chemistries that are dictated by the nature and order of the deposition processes.

No abstract