Comparative electron spin resonance study of epi-Lu2O3/(111)Si and a-Lu2O3/(100)Si interfaces: Misfit point defects

Abstract

An electron spin resonance study has been carried out on heteroepitaxial Si/insulator structures obtained through growth of epi-Lu 2 O 3 films on ͑111͒Si ͑ϳ4.5% mismatch͒ by molecular-beam epitaxy, with special attention to the inherent quality as well as the thermal stability of interfaces, monitored through occurring paramagnetic point defects. This indicates the presence, in the as-grown state, of P b defects ͑ϳ5 ϫ 10 11 cm −2 ͒ with the unpaired sp 3 Si dangling bond along the ͓111͔ interface normal, the archetypical defect ͑trap͒ of the standard thermal ͑111͒Si/ SiO 2 interface, directly revealing, and identified as the result of, imperfect epitaxy. The occurrence of P b defects, a major system of electrically detrimental interface traps, is ascribed to lattice mismatch with related introduction of misfit dislocations. This interface nature appears to persist for annealing in vacuum up to a temperature T an ϳ 420°C. Yet, in the range T an ϳ 420-550°C, the interface starts to "degrade" to standard Si/ SiO 2 properties, as indicated by the gradually increasing P b density and attendant appearance of the EX center, an SiO 2-associated defect. At T an ϳ 700°C, ͓P b ͔ has increased to about 1.3 times the value for standard thermal ͑111͒Si/ SiO 2 , to remain constant up to T an ϳ 1000°C, indicative of an unaltered interface structure. Annealing at T an Ͼ 1000°C results in disintegration altogether of the Si/ SiO 2-type interface. Passivation anneal in H 2 ͑405°C͒ alarmingly fails to deactivate the P b system to the device grade ͑sub͒ 10 10 cm −2 eV −1 level, which would disfavor c-Lu 2 O 3 as a suitable future high-replacement for the a-SiO 2 gate dielectric. Comparison of the thermal stability of the c-Lu 2 O 3 / ͑111͒Si interface with that of molecular-beam deposited amorphous-Lu 2 O 3 / ͑100͒Si shows the former to be superior, yet unlikely to meet technological thermal budget requirements. No Lu 2 O 3-specific point defects could be observed.

Growth of Ta2SnO6 Films, a Candidate Wide-Band-Gap p-Type Oxide

“…Surprisingly, based on the intensity of diffraction peaks in Figure b,d, there appears to be a slight preference for the twinned orientation of Ta 2 SnO 6 in which the rutile Ta 2 O 5 sublattice is oriented differently from the rutile substrate versus the untwinned orientation where they have the same orientation. This is analogous to the A -type (same orientation) and B -type (180° in-plane rotation) twins seen in metal disilicides formed on Si(111) , and in the epitaxial growth of bixbyites on Si(111). − For these latter examples, it is also common for the dominant twin to be the one that is 180° rotated from following the motif of the underlying substrate, i.e., B -type.…”

Functionality of thermally hydrogen-passivated interfaces of oxidized crystalline arrays of Si nanowires on (100)Si

“…Thus, for any Si/SiO 2 -based device manufacturing, it is important to ascertain from the onset an as low as possible density of (non-passivated) interfacial Si DBs sites (P b -type centers). This advice appears not to be different for other Si interfaces such as Si/high-κ oxides (κ is the dielectric constant) [6]. Conventional room temperature (RT) ESR has been carried out before on Si NWs with a crystalline (c-) Si core, either hydrogen terminated or covered with an oxide, for various preparation methods [7][8][9][10], yet no crystalline information could be extracted.…”