Abstract One or more monolayers of cerium arrayed on the surface of a niobium metal acts as a catalyst to oxidation of the niobium at ambient temperature and results in a very thin, very high quality insulating layer which may be configured by patterning of the catalyst. Significant amounts of Nb 2 O 5 are formed at pressures as low as 6.6×10 -6 Pa, promoted by the presence of the cerium. This catalytic activity is related to the trivalent to tetravalent valence change of the cerium during oxidation. The kinetics of Nb 2 O 5 formation beneath the oxidized cerium shows two stages: the first stage is fast growth limited by ion diffusion; the second stage is slow growth limited by electron tunneling. Other catalytic rare earths usable instead of cerium are terbium and praseodymium; other substrate materials usable instead of niobium are aluminum, hafnium, silicon and tantalum, or oxidizable alloys thereof.
A method for controllably preparing high quality insulating oxide layers on a solid surface of material not normally oxidizable to useful quality or thickness at ambient temperatures within acceptable process time durations characterized by (a) depositing a very thin layer, 1-10 monolayers, of a rare earth having catalytic activity related to valence increase during oxidation; and (b) exposing to oxygen in a humidity-free atmosphere for a duration and at an oxygen partial pressure required to grow the desired oxide thickness at ambient or slightly elevated temperature; whereby oxide layers are grown below threshold values for oxidation of equivalent parameters absent catalytic activity.
Claim 2
Independent Claim
102 words
A method for controllably preparing high quality insulating oxide layers on a solid surface of material not normally oxidizable to useful quality or thickness at ambient temperatures within acceptable process time durations characterized by (a) depositing a very thin layer, 1-10 monolayers, of a rare earth having catalytic activity related to valence increase during oxidation; and (b) exposing to oxygen in a humidity-free atmosphere for a duration and at an oxygen partial pressure required to grow the desired oxide thickness at ambient or slightly elevated temperature; whereby oxide layers are grown below threshold values for oxidation of equivalent parameters absent catalytic activity.
Claim 3
Dependent Claim
20 words
The method of claim 1, wherein said very thin layer of catalyst is cerium of thickness less than 3 nm.
Claim 4
Dependent Claim
20 words
The method of claim 1, wherein said very thin layer of catalyst is terbium of thickness less than 3 nm.
Claim 5
Dependent Claim
20 words
The method of claim 1, wherein said very thin layer of catalyst is praseodymium of thickness less than 3 nm.
Claim 6
Dependent Claim
25 words
The method of claim 1, wherein said solid surface of material not normally oxidizable is one or an alloy of aluminum, hafnium, silicon or tantalum.
Claim 7
Dependent Claim
16 words
The method of claim 1, further characterized in that said catalyst is configured in a pattern.