We report large (>10%) magnetization modulation by ferroelectric polarization reversal in the ferroelectric-ferromagnetic BaTiO3/La0.67Sr0.33MnO3 (BTO/LSMO) heterostructures. We find that the electrically induced change in magnetization is limited to the BTO/LSMO interface but extends about 3 nm deep into the LSMO layer—far beyond the expected screening length of metallic LSMO. It is suggested that this effect is due to a metal-insulator transition occurring at the BTO/LSMO interface as a result of electrostatic doping.

We find a pyroelectric current along the 110 direction of stoichiometric Li 2 B 4 O 7 so that the pyroelectric coefficient is nonzero but roughly 10 −3 smaller than along the 001 direction of spontaneous polarization. Abrupt decreases in the pyroelectric coefficient along the 110 direction can be correlated with anomalies in the elastic stiffness C D 33 contributing to concept that the pyroelectric coefficient is not simply a vector but has qualities of a tensor, as expected. The time dependent surface photovoltaic charging suggests that an inverse piezoelectric effect occurs at the (110) surface but not the (100) surface. Both effects along the 110 direction or at the (110) surface are distinct the conventional as a bulk pyroelectric effect.

The band structure of Li2B4O7(100) and Li2B4O7(110) was experimentally determined using a combination of angle-resolved photoemission and angle-resolved inverse photoemission spectroscopies. The experimental band gap depends on crystallographic direction but exceeds 8.8 eV, while the bulk band gap is believed to be in the vicinity of 9.8 eV, in qualitative agreement with expectations. The occupied bulk band structure indicates relatively large values for the hole mass; with the hole mass as significantly larger than that of the electron mass derived from the unoccupied band structure. The Li2B4O7(110) surface is characterized by a very light mass image potential state and a surface state that falls within the band gap of the projected bulk band structure.

No abstract

Gd-doped HfO 2 films were deposited on p-type silicon substrates in a reducing atmosphere. Photoemission measurements indicate the ntype character of Gd-doped HfO 2 due to overcompensation with oxygen vacancies. The Gd 4 f photoexcitation peak at 5.5 eV below the valence band max imum is identified using both resonant photoemission and first-principles calculations of the f hole. The rectifying (diode-like) properties of Gd-doped HfO 2 to silicon heterojunctions are demonstrated.PACS 68.55.Ln; 29.40.Wk; 81.05.Je ________________________________________ While HfO 2 has attracted considerable attention as a high-κ dielectric oxide [1][2][3][4], the gadolinium doping of a number of wide band gap semiconductors [5][6][7][8][9] suggests that Gd doping of HfO 2 may also lead to a dilute magnetic semiconduc tor [10,11]. Moreover, semiconducting Gd-doped HfO 2 may provide a promising new class of materials for neutron detec tion technologies.A gadolinium-based semiconductor diode might be better for neutron detection because of the large thermal neutron absorption cross section of gadolinium (on average ~ 46,000barns). The 157 Gd(n,γ)→ 158 Gd and 155 Gd(n,γ)→ 156 Gd reactions lead to the emission of low-energy gamma rays and conversion electrons, most of which are emit ted at energies below 220 eV [12][13][14][15]. The appeal of using 157 Gd is due to its large thermal neutron cross section of 240 000 barns [16,17]. Although sensitive to gamma radia tion, the big advantage of gadolinium over boron is not only the high neutron capture cross section but also that this cross section extends to higher neutron energies (200 meV)thanis the case for boron. While all-boron-carbide neutron detectors have been demonstrated [18][19][20], and their potential detection efficiency is much higher than that of many semiconductor materials (likely well above 50% for 10 B-enriched devices), the drawback to all boron-based devices is the need for a mod erator to reduce the neutron kinetic energies to 25-30 meV. Fissile radiation sources like 235 U or 239 Pu produce 1-2MeV neutrons, so the moderator must be significant.Since neutron capture by gadolinium leads to production of a conversion electron, the pulse height will be smaller than in the case of neutron capture by boron (10 4 charges versus 10 6 per neutron capture). Accordingly, it is advantageous to see if a Gd-doped HfO 2 diode can be fabricated that can be impedance matched and compatible with a high gain, low noise amplifier. A heterojunction diode with silicon would serve this purpose. Although Gd is expected to be a p-type dopant in HfO 2 , we attempted to fabricate a heterojunction diode of n-type Gd-doped HfO 2 with silicon by overcompen sating the Gd acceptor states by donor states introduced by oxygen vacancies, as such a device would likely have a larger depletion region and therefore larger detection volume.The Gd-doped (3 at. %) HfO 2 films were deposited on single crystal silicon (100) p-type substrates using pulsed laser deposition (PLD) at a growth rate of a...