Hannah J Joyce

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We demonstrate vertically aligned epitaxial GaAs nanowires of excellent crystallographic quality and optimal shape, grown by Au nanoparticle-catalyzed metalorganic chemical vapor deposition. This is achieved by a two-temperature growth procedure, consisting of a brief initial high-temperature growth step followed by prolonged growth at a lower temperature.(More)
Graphene is a single layer of covalently bonded carbon atoms, which was discovered only 8 years ago and yet has already attracted intense research and commercial interest. Initial research focused on its remarkable electronic properties, such as the observation of massless Dirac fermions and the half-integer quantum Hall effect. Now graphene is finding(More)
Antibody levels specific for capsular polysaccharides of Streptococcus pneumoniae and Haemophilus influenzae type b (Hib) and to tetanus toxoid (TT), were measured in serum samples of 750 age-stratified subjects from the UK. The study subjects comprised healthy adult volunteers and hospitalized children undergoing elective surgery, excluding those with a(More)
Controlling the crystallographic phase purity of III-V nanowires is notoriously difficult, yet this is essential for future nanowire devices. Reported methods for controlling nanowire phase require dopant addition, or a restricted choice of nanowire diameter, and only rarely yield a pure phase. Here we demonstrate that phase-perfect nanowires, of arbitrary(More)
It is questionable as to whether a low serum concentration of one of the IgG subclasses identifies a disease state. A low IgG(1) concentration is found in primary or secondary immunodeficiency states but does not occur in isolation. Low IgG(2) concentration is associated with an increased risk of bacterial infections but only in some individuals and not in(More)
We have synthesized ternary InGaAs nanowires on (111)B GaAs surfaces by metal-organic chemical vapor deposition. Au colloidal nanoparticles were employed to catalyze nanowire growth. We observed the strong influence of nanowire density on nanowire height, tapering, and base shape specific to the nanowires with high In composition. This dependency was(More)
Children and adults can have recurrent infection with invasive encapsulated bacterial pathogens such as Streptococcus pneumoniae as a result of a selective inability to respond to polysaccharide antigens. We have identified a mutation in the gene encoding Bruton's tyrosine kinase in a male patient with selective anti-polysaccharide antibody deficiency.
In conventional planar growth of bulk III-V materials, a slow growth rate favors high crystallographic quality, optical quality, and purity of the resulting material. Surprisingly, we observe exactly the opposite effect for Au-assisted GaAs nanowire growth. By employing a rapid growth rate, the resulting nanowires are markedly less tapered, are free of(More)
Using transient terahertz photoconductivity measurements, we have made noncontact, room temperature measurements of the ultrafast charge carrier dynamics in InP nanowires. InP nanowires exhibited a very long photoconductivity lifetime of over 1 ns, and carrier lifetimes were remarkably insensitive to surface states despite the large nanowire surface(More)