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Synthetic single crystal diamonds are irradiated with 100 MeV carbon-ion and characterized by measurements of the X-ray lattice parameter and diffuse scattering (XDS) at room temperature. The lattice parameter increases with the ion fluence. The intensity of XDS diffuses asymmetrically to form a streak along the [-1 0 0] direction parallel to the reciprocal lattice vector. These results suggest that interstitial atoms induced by irradiation aggregate to form dislocation loop on the (1 0 0) plane in the synthetic single crystal diamonds. The results are similar to the XDS of boron-doped single crystal diamond suggesting that boron atoms are likely to form precipitates on the (1 0 0) plane. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Natural and synthetic single crystal diamonds (types Ia, Ib, IIa and IIb) have been characterized by measurements of the X-ray integrated scattering intensity, lattice parameter and diffuse scattering. We found a drastic increase of X-ray integrated scattering intensity for natural and B-doped diamond crystals. Synthetic type IIa diamond was also measured for comparison. Measurements of the lattice parameters have been made at room temperature by using the X-ray bond method. We found that the lattice parameter is smallest for natural diamond and largest for the B-doped diamond. Diffuse scattering experiments were performed using a four circle diffractometer at room temperature. We measured the diffuse scattering for (4 0 0) Bragg reflection for the four types of crystals. The scattering intensity of the natural crystals diffuses asymmetrically to form a streak along the [1 0 0] direction parallel to the reciprocal lattice vector. These results suggest the existence of the nitrogen atom platelets on (1 0 0) plane in the natural diamond. We also found the diffuse streaks along the [ 1 ˙ 0 0 ] direction for (4 0 0) Bragg reflection for the B-doped crystal, suggesting that boron atoms are likely to form precipitates on the (1 0 0) plane.

The lattice parameter of a single-crystal boron-doped synthetic diamond has been measured in the range 4.2-300 K by x-ray diffraction (Bond method), with precision . Over the whole range the results are consistent with A, where T is the absolute temperature. The dilation due to doping indicates a boron concentration of about 100 ppm. The increase of thermal expansion over that of an undoped synthetic diamond is found to be unexpectedly large (10-15%), giving an apparent dilation on doping that is markedly temperature dependent.

Measurements of lattice parameters were made for a single crystal of a high-purity synthetic diamond using the x-ray-diffraction Bond method between 4.2 and 300 K. The key features of the present measurement are as follows: (1) The lattice parameter is determined with an accuracy of ${10}^{\ensuremath{-}6}.$ (2) A very small negative thermal expansion is detected between 30 and 90 K. (3) Thermal expansion shows a behavior of the ${T}^{4}$ law represented by the Debye theory within the measuring temperature range. By comparing the present results with the previously reported results for nitrogen-doped diamond and boron-doped diamond, it is found that diamond becomes harder following doping by nitrogen.

Synthetic single crystal diamonds were irradiated with 100 MeV carbon ions up to a fluence of 3.6×10 15 ions/cm 2 at about 100 K and with 3 MeV electrons up to 1×10 19 e/cm 2 at 60°C. Volume changes after irradiation were studied by means of lattice parameter measurements by X-ray diffraction, indicating linear increases of the lattice parameter with fluence. A drastic increase of the integrated intensity of the scattered X-ray was observed after ion irradiation, and a large increase after electron irradiation. The drastic change is due to the so-called “disappearance of the extinction effects” in the dynamical diffraction theory, which is associated with the introduction of defects by the irradiation. The integrated scattering intensity in diamond is very sensitive to the amount of defects produced by the irradiation.

Precision lattice parameter in La1.85Sr0.15CuO4 single crystal superconductor has been measured in a wide temperature range between 4.2 K and room temperature by the X-ray Bond’s method. An anomalous lattice contraction associated with the appearance of the superconductivity was found in c-plane. Along c-direction, on the contrary, an anomalous expansion of the lattice was observed. The relative spontaneous change in the lattice parameter in c-plane was 2.3xl0­-5 and that of c-axis was 1.5×l0-5 at 4.2 K. The temperature dependence of the spontaneous lattice change was compared with currently existing theories for high Tc superconductivity.

Lattice parameter measurements have been made in a La1.85Sr0.15CuO4 single crystal superconductor between 4.2 K and room temperature by the X-ray Bond method. A structural distortion near the superconducting transition temperature of 33 K has been observed. The lattice spacing in the c-direction increases below the superconducting transition temperature with decreasing temperature. The change in the lattice parameter, Δc/c0, between 4.2 K and 33 K, is 2×10−5. Along a direction perpendicular to the c-axis, on other hand, the lattice spacing decreases more rapidly than expected from normal thermal contraction. The possible importance of these results for existing theories of high temperature superconductivity is noted.

The lattice parameter of synthetic diamond single crystals has been measured in the range 4.2-320 K by the X-ray diffraction method. The lattice parameter is found to be nearly constant between 4.2 and 90 K. The thermal expansion coefficient α calculated from the experimental results is very small (of the order of 10-7 or less) and no definite evidence of the negative thermal expansion is found within our relative experimental accuracy of the order of ±1×10-6.

The thermal expansion of the lattice constant of a GaP crystal was measured in the range 4.2-300K using the Bond method. The authors found a negative thermal expansion coefficient for GaP at low temperatures. They also calculated the Gruneisen parameter and this was negative below 50K. These experimental results do not agree with the phenomenological theory in which a positive thermal expansion coefficient for GaP is predicted at low temperatures.

The thermal expansion of the lattice constant of InP crystal has been measured in the range 4.2-300 K by the Bond method and the results are shown graphically. The thermal expansion coefficient alpha calculated from the experimental results is negative between 15 and 80 K and positive below 15 K. The corresponding Gruneisen parameter gamma closely follows the behaviour of alpha and the values of alpha and gamma are tabulated and shown graphically. The results do not agree with the phenomenological theory in which only a negative alpha is predicted for InP at low temperatures.