Browse Prior Art Database

Polar Switch

IP.com Disclosure Number: IPCOM000073567D
Original Publication Date: 1971-Jan-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 2 page(s) / 24K

Publishing Venue

IBM

Related People

Esaki, L: AUTHOR [+3]

Abstract

A two terminal device which switches between two conducting states is shown in A. A thin film sandwich of niobium-niobium oxide and bismuth is fabricated by evaporating a niobium strip 1 onto a single crystal sapphire substrate 2 which is held at an elevated temperature. This results in the formation of single crystal niobium. The niobium is then oxidized by controlled anodization to provide a niobium oxide layer 3. Layer 3 of niobium oxide is 30-40 angstroms in thickness. A layer of bismuth 4 is evaporated by well known techniques as a top electrode.

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Polar Switch

A two terminal device which switches between two conducting states is shown in A. A thin film sandwich of niobium-niobium oxide and bismuth is fabricated by evaporating a niobium strip 1 onto a single crystal sapphire substrate 2 which is held at an elevated temperature. This results in the formation of single crystal niobium. The niobium is then oxidized by controlled anodization to provide a niobium oxide layer 3. Layer 3 of niobium oxide is 30-40 angstroms in thickness. A layer of bismuth 4 is evaporated by well known techniques as a top electrode.

When voltage is applied across the sandwich of A, current in the switch is carried primarily by tunneling. The device exhibits low and high resistance characteristics as shown in B. When in the low resistance state, for example, the device remains in that state unless a negative voltage greater than a threshold is applied. When the device of A is in a high resistance state, for example, it will remain there unless a voltage more positive than a threshold is applied. The ratio of the impedances between the two states has been observed to be as high as 10. The effect is observed at 4.2 degrees K and 77 degrees K. The change in tunneling current is believed to be due to a switching of the ferroelectric bismuth niobate which is formed when the device is manufactured and, as such, any thin ferroelectric insulator having the same properties should show similar results. Devices having characteristics shown in...