the present invention consists of a specially designed lid and shield configuration which permits growth of silicon dendritic web at a predetermined width . the configuration also permits some adjustment of the desired width during growth . one embodiment of this configuration is shown in fig3 . as shown , the susceptor lid 15 has a relatively short slot region 16 which provides a hot bridge region 17 to reduce the lateral heat loss , and appropriately sized end holes 19 spaced a predetermined distance from the ends of the slot 16 and adjacent the boundaries of the dendrite web , to control the intrinsic thermal gradient in the melt . as shown in fig3 the slot region 16 connects with an enlarged circular end region 18 . this end region 18 permits symmetrical heat loss around the dendrites , and is generally symmetrical about the dendrite . additional control of the thermal gradient in the melt is provided by the size of the circular end region 18 of the slot 16 . as shown in fig3 the configuration embodies radiation shielding 20 above the lid proper , although the number and spacing of the shields 20 may vary according to other thermal requirements of the growth . as shown in fig3 the radiation shields 20 are configured to fit in register over the top of the susceptor lid 15 such that the slot region 16 , end holes 19 , and end region 18 remain uncovered . the principles embodied in this design are to control width primarily by controlling the lateral heat loss from the edges of the ribbon . if only a short slot 16 is used , then the surface temperature profile of the melt is so dipped as to make the growth unstable even though the lateral loss is not reduced . the addition of the end holes 19 to the design modifies the melt temperature so that a stable growth is possible . the width at which control is achieved is determined by the dimensions of the slot 16 and end holes 19 and the distance the end holes 19 are spaced from the slot 16 . since there may still be a shallow temperature &# 34 ; trough &# 34 ; at the melt surface , the precise crystal width within a small range can be fine tuned by small adjustments of the system temperature . fig4 shows the width as functions of length for a crystal grown using the growth configuration of fig3 . the crystal maintains its width within ± 0 . 5 millimeters for well over a meter of growth . some of the fluctuation which occurred was the result of the same temperature changes made by the operator . other crystals grown with this configuration reproduce the width / length characteristics as shown to lengths of 5 meters of constant width . by intentionally introducing small changes in the system temperature , the crystal may be made to widen or narrow , so that the growth at specific width is achieved without detriment to overall growth stability . the example discussed above and illustrated in fig3 should not be construed to impose limitations on the concept of this invention . other configurations embodying this concept may be used to control the width of the web crystal . a few examples of other lid slot geometries are shown in fig5 . each of these configurations permit control of the heat loss pattern in the region of the web crystal , the bounding dendrites and over the melt surface in and beyond the web growth region by adjusting the size and shape of the slot pattern , and thus represent passive control of the web width . as shown in fig5 all of the lid slot geometries have several things in common . first , each comprises a slot region 16a - e bounded on either end by end regions 18a - e . while these end regions were previously described as circular , as shown in fig5 they may be oblong , diamond - shaped , oval , or any other shape which suits the particular application . in any event , the end regions 18a - e are generally symmetrical about the boundaries of the web . also , as shown in fig5 each of the lid slot geometries contains end holes 19a - e . again , these end holes may , but need not , be circular . for example , fig5 b and 5c demonstrate oval end holes . additionally , it would be possible to practice the present invention by providing more than one end hole 19 at each end of the slot 16 . as shown in fig5 c through 5e , the end holes 19 are joined to the end region 18 by means of a secondary slot region 21c - e . as shown , this secondary slot region 21 may be of varying width depending on the particular needs of the system . another method of carrying out the present invention is demonstrated in fig6 . for example , given a configuration which produces the desired temperature profile in the melt , the heat loss pattern from the dendrites can be controlled by adding heat to the dendrite edge 11 with a focused radiative heat source 22 , thus decreasing the losses from the dendrite edge 11 in order to approach a more symmetrical heat loss pattern from the dendrite tip . as shown in fig7 the heat loss pattern can also be altered by increasing the heat losses from the dendrite faces 23 using gas jets 24 . as shown , the gas jets 24 can be used to cool the dendrite faces 23 in order to approach symmetrical heat loss conditions around the dendrite . fig8 represents a top view of a typical dendritic web system with dendrites 10 being pulled through the slot 16 in the susceptor lid 15 . as shown in fig8 radiation ports 25 in the susceptor lid 15 can also be used to increase losses from the dendrite faces 23 . as shown , these radiation ports 25 extend outwardly from the slot 16 of the susceptor lid 15 to the outer edge 33 of the susceptor lid . the radiation ports , as shown , extend from a region in the slot 16 adjacent the region through which the dendrites , or boundaries of the dendritic web , are pulled . radiation ports could also be positioned along the sides of the susceptor , positioned adjacent the dendritic web boundaries to further control temperature gradients at the boundaries . inversely , given a slot design which controls the heat loss pattern from the dendrites , the temperature distribution in the melt could be controlled with radiation ports 27 extending out the bottom of the susceptor 28 or by appropriate radiation shielding , as shown in fig9 . as shown in fig9 the radiation ports 27 extend from the susceptor cavity 29 through the susceptor bottom 34 . the radiation ports 27 permit heat loss from the melt , and are positioned at a location in the susceptor 28 such that the melt temperature profiles in the melt can be controlled . as shown in fig8 and 9 , this location generally coincides with the location of the end holes 19 in the susceptor lid 15 .